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postgresql/src/backend/commands/statscmds.c

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Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
/*-------------------------------------------------------------------------
*
* statscmds.c
Standardize terminology for pg_statistic_ext entries. Consistently refer to such an entry as a "statistics object", not just "statistics" or "extended statistics". Previously we had a mismash of terms, accompanied by utter confusion as to whether the term was singular or plural. That's not only grating (at least to the ear of a native English speaker) but could be outright misleading, eg in error messages that seemed to be referring to multiple objects where only one could be meant. This commit fixes the code and a lot of comments (though I may have missed a few). I also renamed two new SQL functions, pg_get_statisticsextdef -> pg_get_statisticsobjdef pg_statistic_ext_is_visible -> pg_statistics_obj_is_visible to conform better with this terminology. I have not touched the SGML docs other than fixing those function names; the docs certainly need work but it seems like a separable task. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-14 16:54:47 +02:00
* Commands for creating and altering extended statistics objects
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
*
Update copyright for 2024 Reported-by: Michael Paquier Discussion: https://postgr.es/m/ZZKTDPxBBMt3C0J9@paquier.xyz Backpatch-through: 12
2024-01-04 02:49:05 +01:00
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/commands/statscmds.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
Replace heapam.h includes with {table, relation}.h where applicable. A lot of files only included heapam.h for relation_open, heap_open etc - replace the heapam.h include in those files with the narrower header. Author: Andres Freund Discussion: https://postgr.es/m/20190111000539.xbv7s6w7ilcvm7dp@alap3.anarazel.de
2019-01-21 19:18:20 +01:00
#include "access/relation.h"
#include "access/table.h"
Remove WITH OIDS support, change oid catalog column visibility. Previously tables declared WITH OIDS, including a significant fraction of the catalog tables, stored the oid column not as a normal column, but as part of the tuple header. This special column was not shown by default, which was somewhat odd, as it's often (consider e.g. pg_class.oid) one of the more important parts of a row. Neither pg_dump nor COPY included the contents of the oid column by default. The fact that the oid column was not an ordinary column necessitated a significant amount of special case code to support oid columns. That already was painful for the existing, but upcoming work aiming to make table storage pluggable, would have required expanding and duplicating that "specialness" significantly. WITH OIDS has been deprecated since 2005 (commit ff02d0a05280e0). Remove it. Removing includes: - CREATE TABLE and ALTER TABLE syntax for declaring the table to be WITH OIDS has been removed (WITH (oids[ = true]) will error out) - pg_dump does not support dumping tables declared WITH OIDS and will issue a warning when dumping one (and ignore the oid column). - restoring an pg_dump archive with pg_restore will warn when restoring a table with oid contents (and ignore the oid column) - COPY will refuse to load binary dump that includes oids. - pg_upgrade will error out when encountering tables declared WITH OIDS, they have to be altered to remove the oid column first. - Functionality to access the oid of the last inserted row (like plpgsql's RESULT_OID, spi's SPI_lastoid, ...) has been removed. The syntax for declaring a table WITHOUT OIDS (or WITH (oids = false) for CREATE TABLE) is still supported. While that requires a bit of support code, it seems unnecessary to break applications / dumps that do not use oids, and are explicit about not using them. The biggest user of WITH OID columns was postgres' catalog. This commit changes all 'magic' oid columns to be columns that are normally declared and stored. To reduce unnecessary query breakage all the newly added columns are still named 'oid', even if a table's column naming scheme would indicate 'reloid' or such. This obviously requires adapting a lot code, mostly replacing oid access via HeapTupleGetOid() with access to the underlying Form_pg_*->oid column. The bootstrap process now assigns oids for all oid columns in genbki.pl that do not have an explicit value (starting at the largest oid previously used), only oids assigned later by oids will be above FirstBootstrapObjectId. As the oid column now is a normal column the special bootstrap syntax for oids has been removed. Oids are not automatically assigned during insertion anymore, all backend code explicitly assigns oids with GetNewOidWithIndex(). For the rare case that insertions into the catalog via SQL are called for the new pg_nextoid() function can be used (which only works on catalog tables). The fact that oid columns on system tables are now normal columns means that they will be included in the set of columns expanded by * (i.e. SELECT * FROM pg_class will now include the table's oid, previously it did not). It'd not technically be hard to hide oid column by default, but that'd mean confusing behavior would either have to be carried forward forever, or it'd cause breakage down the line. While it's not unlikely that further adjustments are needed, the scope/invasiveness of the patch makes it worthwhile to get merge this now. It's painful to maintain externally, too complicated to commit after the code code freeze, and a dependency of a number of other patches. Catversion bump, for obvious reasons. Author: Andres Freund, with contributions by John Naylor Discussion: https://postgr.es/m/20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de
2018-11-21 00:36:57 +01:00
#include "catalog/catalog.h"
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
Allow setting statistics target for extended statistics When building statistics, we need to decide how many rows to sample and how accurate the resulting statistics should be. Until now, it was not possible to explicitly define statistics target for extended statistics objects, the value was always computed from the per-attribute targets with a fallback to the system-wide default statistics target. That's a bit inconvenient, as it ties together the statistics target set for per-column and extended statistics. In some cases it may be useful to require larger sample / higher accuracy for extended statics (or the other way around), but with this approach that's not possible. So this commit introduces a new command, allowing to specify statistics target for individual extended statistics objects, overriding the value derived from per-attribute targets (and the system default). ALTER STATISTICS stat_name SET STATISTICS target_value; When determining statistics target for an extended statistics object we first look at this explicitly set value. When this value is -1, we fall back to the old formula, looking at the per-attribute targets first and then the system default. This means the behavior is backwards compatible with older PostgreSQL releases. Author: Tomas Vondra Discussion: https://postgr.es/m/20190618213357.vli3i23vpkset2xd@development Reviewed-by: Kirk Jamison, Dean Rasheed
2019-09-10 20:09:27 +02:00
#include "catalog/objectaccess.h"
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
#include "catalog/pg_namespace.h"
#include "catalog/pg_statistic_ext.h"
Rework the pg_statistic_ext catalog Since extended statistic got introduced in PostgreSQL 10, there was a single catalog pg_statistic_ext storing both the definitions and built statistic. That's however problematic when a user is supposed to have access only to the definitions, but not to user data. Consider for example pg_dump on a database with RLS enabled - if the pg_statistic_ext catalog respects RLS (which it should, if it contains user data), pg_dump would not see any records and the result would not define any extended statistics. That would be a surprising behavior. Until now this was not a pressing issue, because the existing types of extended statistic (functional dependencies and ndistinct coefficients) do not include any user data directly. This changed with introduction of MCV lists, which do include most common combinations of values. The easiest way to fix this is to split the pg_statistic_ext catalog into two - one for definitions, one for the built statistic values. The new catalog is called pg_statistic_ext_data, and we're maintaining a 1:1 relationship with the old catalog - either there are matching records in both catalogs, or neither of them. Bumped CATVERSION due to changing system catalog definitions. Author: Dean Rasheed, with improvements by me Reviewed-by: Dean Rasheed, John Naylor Discussion: https://postgr.es/m/CAEZATCUhT9rt7Ui%3DVdx4N%3D%3DVV5XOK5dsXfnGgVOz_JhAicB%3DZA%40mail.gmail.com
2019-06-13 17:19:21 +02:00
#include "catalog/pg_statistic_ext_data.h"
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
#include "commands/comment.h"
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
#include "commands/defrem.h"
#include "miscadmin.h"
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
#include "statistics/statistics.h"
Remove unused #include's from backend .c files as determined by include-what-you-use (IWYU) While IWYU also suggests to *add* a bunch of #include's (which is its main purpose), this patch does not do that. In some cases, a more specific #include replaces another less specific one. Some manual adjustments of the automatic result: - IWYU currently doesn't know about includes that provide global variable declarations (like -Wmissing-variable-declarations), so those includes are being kept manually. - All includes for port(ability) headers are being kept for now, to play it safe. - No changes of catalog/pg_foo.h to catalog/pg_foo_d.h, to keep the patch from exploding in size. Note that this patch touches just *.c files, so nothing declared in header files changes in hidden ways. As a small example, in src/backend/access/transam/rmgr.c, some IWYU pragma annotations are added to handle a special case there. Discussion: https://www.postgresql.org/message-id/flat/af837490-6b2f-46df-ba05-37ea6a6653fc%40eisentraut.org
2024-03-04 12:00:11 +01:00
#include "utils/acl.h"
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
#include "utils/builtins.h"
#include "utils/inval.h"
Make the order of the header file includes consistent Similar to commit 7e735035f20. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/CAMbWs4-WhpCFMbXCjtJ%2BFzmjfPrp7Hw1pk4p%2BZpU95Kh3ofZ1A%40mail.gmail.com
2024-03-13 15:07:00 +01:00
#include "utils/lsyscache.h"
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/typcache.h"
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
static char *ChooseExtendedStatisticName(const char *name1, const char *name2,
const char *label, Oid namespaceid);
static char *ChooseExtendedStatisticNameAddition(List *exprs);
Code review for commands/statscmds.c. Fix machine-dependent sorting of column numbers. (Odd behavior would only materialize for column numbers above 255, but that's certainly legal.) Fix poor choice of SQLSTATE for some errors, and improve error message wording. (Notably, "is not a scalar type" is a totally misleading way to explain "does not have a default btree opclass".) Avoid taking AccessExclusiveLock on the associated relation during DROP STATISTICS. That's neither necessary nor desirable, and it could easily have put us into situations where DROP fails (compare commit 68ea2b7f9). Adjust/improve comments. David Rowley and Tom Lane Discussion: https://postgr.es/m/CAKJS1f-GmCfPvBbAEaM5xoVOaYdVgVN1gicALSoYQ77z-+vLbw@mail.gmail.com
2017-04-24 17:15:15 +02:00
/* qsort comparator for the attnums in CreateStatistics */
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
static int
compare_int16(const void *a, const void *b)
{
Code review for commands/statscmds.c. Fix machine-dependent sorting of column numbers. (Odd behavior would only materialize for column numbers above 255, but that's certainly legal.) Fix poor choice of SQLSTATE for some errors, and improve error message wording. (Notably, "is not a scalar type" is a totally misleading way to explain "does not have a default btree opclass".) Avoid taking AccessExclusiveLock on the associated relation during DROP STATISTICS. That's neither necessary nor desirable, and it could easily have put us into situations where DROP fails (compare commit 68ea2b7f9). Adjust/improve comments. David Rowley and Tom Lane Discussion: https://postgr.es/m/CAKJS1f-GmCfPvBbAEaM5xoVOaYdVgVN1gicALSoYQ77z-+vLbw@mail.gmail.com
2017-04-24 17:15:15 +02:00
int av = *(const int16 *) a;
int bv = *(const int16 *) b;
/* this can't overflow if int is wider than int16 */
return (av - bv);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
}
/*
* CREATE STATISTICS
*/
ObjectAddress
CreateStatistics(CreateStatsStmt *stmt)
{
int16 attnums[STATS_MAX_DIMENSIONS];
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
int nattnums = 0;
int numcols;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
char *namestr;
Fix bogus Name assignment in CreateStatistics Apparently, it doesn't work to use a plain cstring as a Name datum: you may end up having random bytes because of failing to zero the bytes after the terminating \0, as indicated by valgrind. I introduced this bug in 5564c1181548, so backpatch this fix to REL_10_STABLE, like that commit. While at it, fix a slightly misleading comment, pointed out by David Rowley.
2018-03-06 17:17:13 +01:00
NameData stxname;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Oid statoid;
Oid namespaceId;
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
Oid stxowner = GetUserId();
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
HeapTuple htup;
Datum values[Natts_pg_statistic_ext];
bool nulls[Natts_pg_statistic_ext];
Rename columns in new pg_statistic_ext catalog The new catalog reused a column prefix "sta" from pg_statistic, but this is undesirable, so change the catalog to use prefix "stx" instead. Also, rename the column that lists enabled statistic kinds as "stxkind" rather than "enabled". Discussion: https://postgr.es/m/CAKJS1f_2t5jhSN7huYRFH3w3rrHfG2QU7hiUHsu-Vdjd1rYT3w@mail.gmail.com
2017-04-17 23:34:29 +02:00
int2vector *stxkeys;
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
List *stxexprs = NIL;
Datum exprsDatum;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Relation statrel;
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
Relation rel = NULL;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Oid relid;
ObjectAddress parentobject,
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
myself;
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
Datum types[4]; /* one for each possible type of statistic */
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
int ntypes;
Rename columns in new pg_statistic_ext catalog The new catalog reused a column prefix "sta" from pg_statistic, but this is undesirable, so change the catalog to use prefix "stx" instead. Also, rename the column that lists enabled statistic kinds as "stxkind" rather than "enabled". Discussion: https://postgr.es/m/CAKJS1f_2t5jhSN7huYRFH3w3rrHfG2QU7hiUHsu-Vdjd1rYT3w@mail.gmail.com
2017-04-17 23:34:29 +02:00
ArrayType *stxkind;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
bool build_ndistinct;
Collect and use multi-column dependency stats Follow on patch in the multi-variate statistics patch series. CREATE STATISTICS s1 WITH (dependencies) ON (a, b) FROM t; ANALYZE; will collect dependency stats on (a, b) and then use the measured dependency in subsequent query planning. Commit 7b504eb282ca2f5104b5c00b4f05a3ef6bb1385b added CREATE STATISTICS with n-distinct coefficients. These are now specified using the mutually exclusive option WITH (ndistinct). Author: Tomas Vondra, David Rowley Reviewed-by: Kyotaro HORIGUCHI, Álvaro Herrera, Dean Rasheed, Robert Haas and many other comments and contributions Discussion: https://postgr.es/m/56f40b20-c464-fad2-ff39-06b668fac47c@2ndquadrant.com
2017-04-06 00:00:42 +02:00
bool build_dependencies;
Add support for multivariate MCV lists Introduce a third extended statistic type, supported by the CREATE STATISTICS command - MCV lists, a generalization of the statistic already built and used for individual columns. Compared to the already supported types (n-distinct coefficients and functional dependencies), MCV lists are more complex, include column values and allow estimation of much wider range of common clauses (equality and inequality conditions, IS NULL, IS NOT NULL etc.). Similarly to the other types, a new pseudo-type (pg_mcv_list) is used. Author: Tomas Vondra Reviewed-by: Dean Rasheed, David Rowley, Mark Dilger, Alvaro Herrera Discussion: https://postgr.es/m/dfdac334-9cf2-2597-fb27-f0fb3753f435@2ndquadrant.com
2019-03-27 18:32:18 +01:00
bool build_mcv;
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
bool build_expressions;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
bool requested_type = false;
Code review for commands/statscmds.c. Fix machine-dependent sorting of column numbers. (Odd behavior would only materialize for column numbers above 255, but that's certainly legal.) Fix poor choice of SQLSTATE for some errors, and improve error message wording. (Notably, "is not a scalar type" is a totally misleading way to explain "does not have a default btree opclass".) Avoid taking AccessExclusiveLock on the associated relation during DROP STATISTICS. That's neither necessary nor desirable, and it could easily have put us into situations where DROP fails (compare commit 68ea2b7f9). Adjust/improve comments. David Rowley and Tom Lane Discussion: https://postgr.es/m/CAKJS1f-GmCfPvBbAEaM5xoVOaYdVgVN1gicALSoYQ77z-+vLbw@mail.gmail.com
2017-04-24 17:15:15 +02:00
int i;
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
ListCell *cell;
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
ListCell *cell2;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Assert(IsA(stmt, CreateStatsStmt));
Reduce lock level for CREATE STATISTICS In line with other lock reductions related to planning. Simon Riggs
2017-04-06 00:22:32 +02:00
/*
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
* Examine the FROM clause. Currently, we only allow it to be a single
* simple table, but later we'll probably allow multiple tables and JOIN
* syntax. The grammar is already prepared for that, so we have to check
* here that what we got is what we can support.
Reduce lock level for CREATE STATISTICS In line with other lock reductions related to planning. Simon Riggs
2017-04-06 00:22:32 +02:00
*/
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
if (list_length(stmt->relations) != 1)
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
ereport(ERROR,
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("only a single relation is allowed in CREATE STATISTICS")));
foreach(cell, stmt->relations)
{
Node *rln = (Node *) lfirst(cell);
if (!IsA(rln, RangeVar))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("only a single relation is allowed in CREATE STATISTICS")));
/*
* CREATE STATISTICS will influence future execution plans but does
* not interfere with currently executing plans. So it should be
* enough to take only ShareUpdateExclusiveLock on relation,
* conflicting with ANALYZE and other DDL that sets statistical
* information, but not with normal queries.
*/
rel = relation_openrv((RangeVar *) rln, ShareUpdateExclusiveLock);
/* Restrict to allowed relation types */
if (rel->rd_rel->relkind != RELKIND_RELATION &&
rel->rd_rel->relkind != RELKIND_MATVIEW &&
rel->rd_rel->relkind != RELKIND_FOREIGN_TABLE &&
rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
Improve error messages about mismatching relkind Most error messages about a relkind that was not supported or appropriate for the command was of the pattern "relation \"%s\" is not a table, foreign table, or materialized view" This style can become verbose and tedious to maintain. Moreover, it's not very helpful: If I'm trying to create a comment on a TOAST table, which is not supported, then the information that I could have created a comment on a materialized view is pointless. Instead, write the primary error message shorter and saying more directly that what was attempted is not possible. Then, in the detail message, explain that the operation is not supported for the relkind the object was. To simplify that, add a new function errdetail_relkind_not_supported() that does this. In passing, make use of RELKIND_HAS_STORAGE() where appropriate, instead of listing out the relkinds individually. Reviewed-by: Michael Paquier <michael@paquier.xyz> Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://www.postgresql.org/message-id/flat/dc35a398-37d0-75ce-07ea-1dd71d98f8ec@2ndquadrant.com
2021-07-08 09:38:52 +02:00
errmsg("cannot define statistics for relation \"%s\"",
RelationGetRelationName(rel)),
errdetail_relkind_not_supported(rel->rd_rel->relkind)));
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
/* You must own the relation to create stats on it */
Refactor ownercheck functions Instead of dozens of mostly-duplicate pg_foo_ownercheck() functions, write one common function object_ownercheck() that can handle almost all of them. We already have all the information we need, such as which system catalog corresponds to which catalog table and which column is the owner column. Reviewed-by: Corey Huinker <corey.huinker@gmail.com> Reviewed-by: Antonin Houska <ah@cybertec.at> Discussion: https://www.postgresql.org/message-id/flat/95c30f96-4060-2f48-98b5-a4392d3b6066@enterprisedb.com
2022-11-13 08:11:17 +01:00
if (!object_ownercheck(RelationRelationId, RelationGetRelid(rel), stxowner))
Replace AclObjectKind with ObjectType AclObjectKind was basically just another enumeration for object types, and we already have a preferred one for that. It's only used in aclcheck_error. By using ObjectType instead, we can also give some more precise error messages, for example "index" instead of "relation". Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
2017-12-02 15:26:34 +01:00
aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(rel->rd_rel->relkind),
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
RelationGetRelationName(rel));
Disallow CREATE STATISTICS on system catalogs Add a check that CREATE STATISTICS does not add extended statistics on system catalogs, similarly to indexes etc. It can be overriden using the allow_system_table_mods GUC. This bug exists since 7b504eb282c, adding the extended statistics, so backpatch all the way back to PostgreSQL 10. Author: Tomas Vondra Reported-by: Dean Rasheed Backpatch-through: 10 Discussion: https://postgr.es/m/CAEZATCXAPrrOKwEsyZKQ4uzzJQWBCt6QAvOcgqRGdWwT1zb%2BrQ%40mail.gmail.com
2021-01-15 23:24:19 +01:00
/* Creating statistics on system catalogs is not allowed */
if (!allowSystemTableMods && IsSystemRelation(rel))
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied: \"%s\" is a system catalog",
RelationGetRelationName(rel))));
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
}
Assert(rel);
relid = RelationGetRelid(rel);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
/*
* If the node has a name, split it up and determine creation namespace.
Make the name optional in CREATE STATISTICS. This allows users to omit the statistics name in a CREATE STATISTICS command, letting the system auto-generate a sensible, unique name, putting the statistics object in the same schema as the table. Simon Riggs, reviewed by Matthias van de Meent. Discussion: https://postgr.es/m/CANbhV-FGD2d_C3zFTfT2aRfX_TaPSgOeKES58RLZx5XzQp5NhA@mail.gmail.com
2022-07-21 20:23:13 +02:00
* If not, put the object in the same namespace as the relation, and cons
* up a name for it. (This can happen either via "CREATE STATISTICS ..."
* or via "CREATE TABLE ... (LIKE)".)
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
*/
if (stmt->defnames)
Fix bogus Name assignment in CreateStatistics Apparently, it doesn't work to use a plain cstring as a Name datum: you may end up having random bytes because of failing to zero the bytes after the terminating \0, as indicated by valgrind. I introduced this bug in 5564c1181548, so backpatch this fix to REL_10_STABLE, like that commit. While at it, fix a slightly misleading comment, pointed out by David Rowley.
2018-03-06 17:17:13 +01:00
namespaceId = QualifiedNameGetCreationNamespace(stmt->defnames,
&namestr);
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
else
{
namespaceId = RelationGetNamespace(rel);
namestr = ChooseExtendedStatisticName(RelationGetRelationName(rel),
ChooseExtendedStatisticNameAddition(stmt->exprs),
"stat",
namespaceId);
}
Fix bogus Name assignment in CreateStatistics Apparently, it doesn't work to use a plain cstring as a Name datum: you may end up having random bytes because of failing to zero the bytes after the terminating \0, as indicated by valgrind. I introduced this bug in 5564c1181548, so backpatch this fix to REL_10_STABLE, like that commit. While at it, fix a slightly misleading comment, pointed out by David Rowley.
2018-03-06 17:17:13 +01:00
namestrcpy(&stxname, namestr);
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
/*
* Deal with the possibility that the statistics object already exists.
*/
if (SearchSysCacheExists2(STATEXTNAMENSP,
CStringGetDatum(namestr),
ObjectIdGetDatum(namespaceId)))
{
if (stmt->if_not_exists)
{
In extensions, don't replace objects not belonging to the extension. Previously, if an extension script did CREATE OR REPLACE and there was an existing object not belonging to the extension, it would overwrite the object and adopt it into the extension. This is problematic, first because the overwrite is probably unintentional, and second because we didn't change the object's ownership. Thus a hostile user could create an object in advance of an expected CREATE EXTENSION command, and would then have ownership rights on an extension object, which could be modified for trojan-horse-type attacks. Hence, forbid CREATE OR REPLACE of an existing object unless it already belongs to the extension. (Note that we've always forbidden replacing an object that belongs to some other extension; only the behavior for previously-free-standing objects changes here.) For the same reason, also fail CREATE IF NOT EXISTS when there is an existing object that doesn't belong to the extension. Our thanks to Sven Klemm for reporting this problem. Security: CVE-2022-2625
2022-08-08 17:12:31 +02:00
/*
* Since stats objects aren't members of extensions (see comments
* below), no need for checkMembershipInCurrentExtension here.
*/
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
ereport(NOTICE,
(errcode(ERRCODE_DUPLICATE_OBJECT),
errmsg("statistics object \"%s\" already exists, skipping",
namestr)));
relation_close(rel, NoLock);
return InvalidObjectAddress;
}
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_OBJECT),
errmsg("statistics object \"%s\" already exists", namestr)));
}
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
/*
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
* Make sure no more than STATS_MAX_DIMENSIONS columns are used. There
* might be duplicates and so on, but we'll deal with those later.
*/
numcols = list_length(stmt->exprs);
if (numcols > STATS_MAX_DIMENSIONS)
ereport(ERROR,
(errcode(ERRCODE_TOO_MANY_COLUMNS),
errmsg("cannot have more than %d columns in statistics",
STATS_MAX_DIMENSIONS)));
/*
* Convert the expression list to a simple array of attnums, but also keep
* a list of more complex expressions. While at it, enforce some
Identify simple column references in extended statistics Until now, when defining extended statistics, everything except a plain column reference was treated as complex expression. So for example "a" was a column reference, but "(a)" would be an expression. In most cases this does not matter much, but there were a couple strange consequences. For example CREATE STATISTICS s ON a FROM t; would fail, because extended stats require at least two columns. But CREATE STATISTICS s ON (a) FROM t; would succeed, because that requirement does not apply to expressions. Moreover, that statistics object is useless - the optimizer will always use the regular statistics collected for attribute "a". So do a bit more work to identify those expressions referencing a single column, and translate them to a simple column reference. Backpatch to 14, where support for extended statistics on expressions was introduced. Reported-by: Justin Pryzby Backpatch-through: 14 Discussion: https://postgr.es/m/20210816013255.GS10479%40telsasoft.com
2021-09-01 17:41:54 +02:00
* constraints - we don't allow extended statistics on system attributes,
Fix typos and grammar in code comments Several mistakes have piled in the code comments over the time, including incorrect grammar, function names and simple typos. This commit takes care of a portion of these. No backpatch is done as this is only cosmetic. Author: Justin Pryzby Discussion: https://postgr.es/m/20210924215827.GS831@telsasoft.com
2021-09-27 07:21:28 +02:00
* and we require the data type to have a less-than operator.
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
*
Fix typos and grammar in code comments Several mistakes have piled in the code comments over the time, including incorrect grammar, function names and simple typos. This commit takes care of a portion of these. No backpatch is done as this is only cosmetic. Author: Justin Pryzby Discussion: https://postgr.es/m/20210924215827.GS831@telsasoft.com
2021-09-27 07:21:28 +02:00
* There are many ways to "mask" a simple attribute reference as an
Identify simple column references in extended statistics Until now, when defining extended statistics, everything except a plain column reference was treated as complex expression. So for example "a" was a column reference, but "(a)" would be an expression. In most cases this does not matter much, but there were a couple strange consequences. For example CREATE STATISTICS s ON a FROM t; would fail, because extended stats require at least two columns. But CREATE STATISTICS s ON (a) FROM t; would succeed, because that requirement does not apply to expressions. Moreover, that statistics object is useless - the optimizer will always use the regular statistics collected for attribute "a". So do a bit more work to identify those expressions referencing a single column, and translate them to a simple column reference. Backpatch to 14, where support for extended statistics on expressions was introduced. Reported-by: Justin Pryzby Backpatch-through: 14 Discussion: https://postgr.es/m/20210816013255.GS10479%40telsasoft.com
2021-09-01 17:41:54 +02:00
* expression, for example "(a+0)" etc. We can't possibly detect all of
Fix typos and grammar in code comments Several mistakes have piled in the code comments over the time, including incorrect grammar, function names and simple typos. This commit takes care of a portion of these. No backpatch is done as this is only cosmetic. Author: Justin Pryzby Discussion: https://postgr.es/m/20210924215827.GS831@telsasoft.com
2021-09-27 07:21:28 +02:00
* them, but we handle at least the simple case with the attribute in
* parens. There'll always be a way around this, if the user is determined
* (like the "(a+0)" example), but this makes it somewhat consistent with
* how indexes treat attributes/expressions.
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
*/
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
foreach(cell, stmt->exprs)
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
{
Replace run-time error check with assertion The error message was checking that the structures returned from the parser matched expectations. That's something we usually use assertions for, not a full user-facing error message. So replace that with an assertion (hidden inside lfirst_node()). Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://www.postgresql.org/message-id/flat/452e9df8-ec89-e01b-b64a-8cc6ce830458%40enterprisedb.com
2021-05-27 09:52:12 +02:00
StatsElem *selem = lfirst_node(StatsElem, cell);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
if (selem->name) /* column reference */
{
char *attname;
Replace run-time error check with assertion The error message was checking that the structures returned from the parser matched expectations. That's something we usually use assertions for, not a full user-facing error message. So replace that with an assertion (hidden inside lfirst_node()). Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://www.postgresql.org/message-id/flat/452e9df8-ec89-e01b-b64a-8cc6ce830458%40enterprisedb.com
2021-05-27 09:52:12 +02:00
HeapTuple atttuple;
Form_pg_attribute attForm;
TypeCacheEntry *type;
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
attname = selem->name;
atttuple = SearchSysCacheAttName(relid, attname);
if (!HeapTupleIsValid(atttuple))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
errmsg("column \"%s\" does not exist",
attname)));
attForm = (Form_pg_attribute) GETSTRUCT(atttuple);
/* Disallow use of system attributes in extended stats */
if (attForm->attnum <= 0)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("statistics creation on system columns is not supported")));
/* Disallow data types without a less-than operator */
type = lookup_type_cache(attForm->atttypid, TYPECACHE_LT_OPR);
if (type->lt_opr == InvalidOid)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("column \"%s\" cannot be used in statistics because its type %s has no default btree operator class",
attname, format_type_be(attForm->atttypid))));
attnums[nattnums] = attForm->attnum;
nattnums++;
ReleaseSysCache(atttuple);
}
Identify simple column references in extended statistics Until now, when defining extended statistics, everything except a plain column reference was treated as complex expression. So for example "a" was a column reference, but "(a)" would be an expression. In most cases this does not matter much, but there were a couple strange consequences. For example CREATE STATISTICS s ON a FROM t; would fail, because extended stats require at least two columns. But CREATE STATISTICS s ON (a) FROM t; would succeed, because that requirement does not apply to expressions. Moreover, that statistics object is useless - the optimizer will always use the regular statistics collected for attribute "a". So do a bit more work to identify those expressions referencing a single column, and translate them to a simple column reference. Backpatch to 14, where support for extended statistics on expressions was introduced. Reported-by: Justin Pryzby Backpatch-through: 14 Discussion: https://postgr.es/m/20210816013255.GS10479%40telsasoft.com
2021-09-01 17:41:54 +02:00
else if (IsA(selem->expr, Var)) /* column reference in parens */
{
Var *var = (Var *) selem->expr;
TypeCacheEntry *type;
/* Disallow use of system attributes in extended stats */
if (var->varattno <= 0)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("statistics creation on system columns is not supported")));
/* Disallow data types without a less-than operator */
type = lookup_type_cache(var->vartype, TYPECACHE_LT_OPR);
if (type->lt_opr == InvalidOid)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("column \"%s\" cannot be used in statistics because its type %s has no default btree operator class",
get_attname(relid, var->varattno, false), format_type_be(var->vartype))));
attnums[nattnums] = var->varattno;
nattnums++;
}
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
else /* expression */
{
Node *expr = selem->expr;
Oid atttype;
Replace run-time error check with assertion The error message was checking that the structures returned from the parser matched expectations. That's something we usually use assertions for, not a full user-facing error message. So replace that with an assertion (hidden inside lfirst_node()). Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://www.postgresql.org/message-id/flat/452e9df8-ec89-e01b-b64a-8cc6ce830458%40enterprisedb.com
2021-05-27 09:52:12 +02:00
TypeCacheEntry *type;
Disallow extended statistics on system columns Since introduction of extended statistics, we've disallowed references to system columns. So for example CREATE STATISTICS s ON ctid FROM t; would fail. But with extended statistics on expressions, it was possible to work around this limitation quite easily CREATE STATISTICS s ON (ctid::text) FROM t; This is an oversight in a4d75c86bf, fixed by adding a simple check. Backpatch to PostgreSQL 14, where support for extended statistics on expressions was introduced. Backpatch-through: 14 Discussion: https://postgr.es/m/20210816013255.GS10479%40telsasoft.com
2021-09-20 00:34:57 +02:00
Bitmapset *attnums = NULL;
int k;
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
Assert(expr != NULL);
Disallow extended statistics on system columns Since introduction of extended statistics, we've disallowed references to system columns. So for example CREATE STATISTICS s ON ctid FROM t; would fail. But with extended statistics on expressions, it was possible to work around this limitation quite easily CREATE STATISTICS s ON (ctid::text) FROM t; This is an oversight in a4d75c86bf, fixed by adding a simple check. Backpatch to PostgreSQL 14, where support for extended statistics on expressions was introduced. Backpatch-through: 14 Discussion: https://postgr.es/m/20210816013255.GS10479%40telsasoft.com
2021-09-20 00:34:57 +02:00
/* Disallow expressions referencing system attributes. */
pull_varattnos(expr, 1, &attnums);
k = -1;
while ((k = bms_next_member(attnums, k)) >= 0)
{
AttrNumber attnum = k + FirstLowInvalidHeapAttributeNumber;
Pre-beta mechanical code beautification. Run pgindent, pgperltidy, and reformat-dat-files. I manually fixed a couple of comments that pgindent uglified.
2022-05-12 21:17:30 +02:00
Disallow extended statistics on system columns Since introduction of extended statistics, we've disallowed references to system columns. So for example CREATE STATISTICS s ON ctid FROM t; would fail. But with extended statistics on expressions, it was possible to work around this limitation quite easily CREATE STATISTICS s ON (ctid::text) FROM t; This is an oversight in a4d75c86bf, fixed by adding a simple check. Backpatch to PostgreSQL 14, where support for extended statistics on expressions was introduced. Backpatch-through: 14 Discussion: https://postgr.es/m/20210816013255.GS10479%40telsasoft.com
2021-09-20 00:34:57 +02:00
if (attnum <= 0)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("statistics creation on system columns is not supported")));
}
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/*
* Disallow data types without a less-than operator.
*
* We ignore this for statistics on a single expression, in which
* case we'll build the regular statistics only (and that code can
* deal with such data types).
*/
if (list_length(stmt->exprs) > 1)
{
atttype = exprType(expr);
type = lookup_type_cache(atttype, TYPECACHE_LT_OPR);
if (type->lt_opr == InvalidOid)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("expression cannot be used in multivariate statistics because its type %s has no default btree operator class",
format_type_be(atttype))));
}
stxexprs = lappend(stxexprs, expr);
}
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
}
/*
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
* Parse the statistics kinds.
*
* First check that if this is the case with a single expression, there
* are no statistics kinds specified (we don't allow that for the simple
* CREATE STATISTICS form).
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
*/
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
if ((list_length(stmt->exprs) == 1) && (list_length(stxexprs) == 1))
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
{
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/* statistics kinds not specified */
Avoid using list_length() to test for empty list. The standard way to check for list emptiness is to compare the List pointer to NIL; our list code goes out of its way to ensure that that is the only representation of an empty list. (An acceptable alternative is a plain boolean test for non-null pointer, but explicit mention of NIL is usually preferable.) Various places didn't get that memo and expressed the condition with list_length(), which might not be so bad except that there were such a variety of ways to check it exactly: equal to zero, less than or equal to zero, less than one, yadda yadda. In the name of code readability, let's standardize all those spellings as "list == NIL" or "list != NIL". (There's probably some microscopic efficiency gain too, though few of these look to be at all performance-critical.) A very small number of cases were left as-is because they seemed more consistent with other adjacent list_length tests that way. Peter Smith, with bikeshedding from a number of us Discussion: https://postgr.es/m/CAHut+PtQYe+ENX5KrONMfugf0q6NHg4hR5dAhqEXEc2eefFeig@mail.gmail.com
2022-08-17 17:12:35 +02:00
if (stmt->stat_types != NIL)
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
ereport(ERROR,
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("when building statistics on a single expression, statistics kinds may not be specified")));
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
}
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/* OK, let's check that we recognize the statistics kinds. */
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
build_ndistinct = false;
Collect and use multi-column dependency stats Follow on patch in the multi-variate statistics patch series. CREATE STATISTICS s1 WITH (dependencies) ON (a, b) FROM t; ANALYZE; will collect dependency stats on (a, b) and then use the measured dependency in subsequent query planning. Commit 7b504eb282ca2f5104b5c00b4f05a3ef6bb1385b added CREATE STATISTICS with n-distinct coefficients. These are now specified using the mutually exclusive option WITH (ndistinct). Author: Tomas Vondra, David Rowley Reviewed-by: Kyotaro HORIGUCHI, Álvaro Herrera, Dean Rasheed, Robert Haas and many other comments and contributions Discussion: https://postgr.es/m/56f40b20-c464-fad2-ff39-06b668fac47c@2ndquadrant.com
2017-04-06 00:00:42 +02:00
build_dependencies = false;
Add support for multivariate MCV lists Introduce a third extended statistic type, supported by the CREATE STATISTICS command - MCV lists, a generalization of the statistic already built and used for individual columns. Compared to the already supported types (n-distinct coefficients and functional dependencies), MCV lists are more complex, include column values and allow estimation of much wider range of common clauses (equality and inequality conditions, IS NULL, IS NOT NULL etc.). Similarly to the other types, a new pseudo-type (pg_mcv_list) is used. Author: Tomas Vondra Reviewed-by: Dean Rasheed, David Rowley, Mark Dilger, Alvaro Herrera Discussion: https://postgr.es/m/dfdac334-9cf2-2597-fb27-f0fb3753f435@2ndquadrant.com
2019-03-27 18:32:18 +01:00
build_mcv = false;
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
foreach(cell, stmt->stat_types)
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
{
Remove useless casts Casting the argument of strVal() to (Value *) is useless, since strVal() already does that. Most code didn't do that anyway; this was apparently just a style that snuck into certain files. Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org> Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/5ba6bc5b-3f95-04f2-2419-f8ddb4c046fb@enterprisedb.com
2021-09-09 07:58:12 +02:00
char *type = strVal(lfirst(cell));
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
if (strcmp(type, "ndistinct") == 0)
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
{
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
build_ndistinct = true;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
requested_type = true;
}
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
else if (strcmp(type, "dependencies") == 0)
Collect and use multi-column dependency stats Follow on patch in the multi-variate statistics patch series. CREATE STATISTICS s1 WITH (dependencies) ON (a, b) FROM t; ANALYZE; will collect dependency stats on (a, b) and then use the measured dependency in subsequent query planning. Commit 7b504eb282ca2f5104b5c00b4f05a3ef6bb1385b added CREATE STATISTICS with n-distinct coefficients. These are now specified using the mutually exclusive option WITH (ndistinct). Author: Tomas Vondra, David Rowley Reviewed-by: Kyotaro HORIGUCHI, Álvaro Herrera, Dean Rasheed, Robert Haas and many other comments and contributions Discussion: https://postgr.es/m/56f40b20-c464-fad2-ff39-06b668fac47c@2ndquadrant.com
2017-04-06 00:00:42 +02:00
{
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
build_dependencies = true;
Collect and use multi-column dependency stats Follow on patch in the multi-variate statistics patch series. CREATE STATISTICS s1 WITH (dependencies) ON (a, b) FROM t; ANALYZE; will collect dependency stats on (a, b) and then use the measured dependency in subsequent query planning. Commit 7b504eb282ca2f5104b5c00b4f05a3ef6bb1385b added CREATE STATISTICS with n-distinct coefficients. These are now specified using the mutually exclusive option WITH (ndistinct). Author: Tomas Vondra, David Rowley Reviewed-by: Kyotaro HORIGUCHI, Álvaro Herrera, Dean Rasheed, Robert Haas and many other comments and contributions Discussion: https://postgr.es/m/56f40b20-c464-fad2-ff39-06b668fac47c@2ndquadrant.com
2017-04-06 00:00:42 +02:00
requested_type = true;
}
Add support for multivariate MCV lists Introduce a third extended statistic type, supported by the CREATE STATISTICS command - MCV lists, a generalization of the statistic already built and used for individual columns. Compared to the already supported types (n-distinct coefficients and functional dependencies), MCV lists are more complex, include column values and allow estimation of much wider range of common clauses (equality and inequality conditions, IS NULL, IS NOT NULL etc.). Similarly to the other types, a new pseudo-type (pg_mcv_list) is used. Author: Tomas Vondra Reviewed-by: Dean Rasheed, David Rowley, Mark Dilger, Alvaro Herrera Discussion: https://postgr.es/m/dfdac334-9cf2-2597-fb27-f0fb3753f435@2ndquadrant.com
2019-03-27 18:32:18 +01:00
else if (strcmp(type, "mcv") == 0)
{
build_mcv = true;
requested_type = true;
}
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
else
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
Message style fixes
2017-09-11 17:20:47 +02:00
errmsg("unrecognized statistics kind \"%s\"",
Change CREATE STATISTICS syntax Previously, we had the WITH clause in the middle of the command, where you'd specify both generic options as well as statistic types. Few people liked this, so this commit changes it to remove the WITH keyword from that clause and makes it accept statistic types only. (We currently don't have any generic options, but if we invent in the future, we will gain a new WITH clause, probably at the end of the command). Also, the column list is now specified without parens, which makes the whole command look more similar to a SELECT command. This change will let us expand the command to supporting expressions (not just columns names) as well as multiple tables and their join conditions. Tom added lots of code comments and fixed some parts of the CREATE STATISTICS reference page, too; more changes in this area are forthcoming. He also fixed a potential problem in the alter_generic regression test, reducing verbosity on a cascaded drop to avoid dependency on message ordering, as we do in other tests. Tom also closed a security bug: we documented that table ownership was required in order to create a statistics object on it, but didn't actually implement it. Implement tab-completion for statistics objects. This can stand some more improvement. Authors: Alvaro Herrera, with lots of cleanup by Tom Lane Discussion: https://postgr.es/m/20170420212426.ltvgyhnefvhixm6i@alvherre.pgsql
2017-05-12 19:59:23 +02:00
type)));
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
}
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/*
* If no statistic type was specified, build them all (but only when the
* statistics is defined on more than one column/expression).
*/
if ((!requested_type) && (numcols >= 2))
Collect and use multi-column dependency stats Follow on patch in the multi-variate statistics patch series. CREATE STATISTICS s1 WITH (dependencies) ON (a, b) FROM t; ANALYZE; will collect dependency stats on (a, b) and then use the measured dependency in subsequent query planning. Commit 7b504eb282ca2f5104b5c00b4f05a3ef6bb1385b added CREATE STATISTICS with n-distinct coefficients. These are now specified using the mutually exclusive option WITH (ndistinct). Author: Tomas Vondra, David Rowley Reviewed-by: Kyotaro HORIGUCHI, Álvaro Herrera, Dean Rasheed, Robert Haas and many other comments and contributions Discussion: https://postgr.es/m/56f40b20-c464-fad2-ff39-06b668fac47c@2ndquadrant.com
2017-04-06 00:00:42 +02:00
{
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
build_ndistinct = true;
Collect and use multi-column dependency stats Follow on patch in the multi-variate statistics patch series. CREATE STATISTICS s1 WITH (dependencies) ON (a, b) FROM t; ANALYZE; will collect dependency stats on (a, b) and then use the measured dependency in subsequent query planning. Commit 7b504eb282ca2f5104b5c00b4f05a3ef6bb1385b added CREATE STATISTICS with n-distinct coefficients. These are now specified using the mutually exclusive option WITH (ndistinct). Author: Tomas Vondra, David Rowley Reviewed-by: Kyotaro HORIGUCHI, Álvaro Herrera, Dean Rasheed, Robert Haas and many other comments and contributions Discussion: https://postgr.es/m/56f40b20-c464-fad2-ff39-06b668fac47c@2ndquadrant.com
2017-04-06 00:00:42 +02:00
build_dependencies = true;
Add support for multivariate MCV lists Introduce a third extended statistic type, supported by the CREATE STATISTICS command - MCV lists, a generalization of the statistic already built and used for individual columns. Compared to the already supported types (n-distinct coefficients and functional dependencies), MCV lists are more complex, include column values and allow estimation of much wider range of common clauses (equality and inequality conditions, IS NULL, IS NOT NULL etc.). Similarly to the other types, a new pseudo-type (pg_mcv_list) is used. Author: Tomas Vondra Reviewed-by: Dean Rasheed, David Rowley, Mark Dilger, Alvaro Herrera Discussion: https://postgr.es/m/dfdac334-9cf2-2597-fb27-f0fb3753f435@2ndquadrant.com
2019-03-27 18:32:18 +01:00
build_mcv = true;
Collect and use multi-column dependency stats Follow on patch in the multi-variate statistics patch series. CREATE STATISTICS s1 WITH (dependencies) ON (a, b) FROM t; ANALYZE; will collect dependency stats on (a, b) and then use the measured dependency in subsequent query planning. Commit 7b504eb282ca2f5104b5c00b4f05a3ef6bb1385b added CREATE STATISTICS with n-distinct coefficients. These are now specified using the mutually exclusive option WITH (ndistinct). Author: Tomas Vondra, David Rowley Reviewed-by: Kyotaro HORIGUCHI, Álvaro Herrera, Dean Rasheed, Robert Haas and many other comments and contributions Discussion: https://postgr.es/m/56f40b20-c464-fad2-ff39-06b668fac47c@2ndquadrant.com
2017-04-06 00:00:42 +02:00
}
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/*
* When there are non-trivial expressions, build the expression stats
* automatically. This allows calculating good estimates for stats that
* consider per-clause estimates (e.g. functional dependencies).
*/
Avoid using list_length() to test for empty list. The standard way to check for list emptiness is to compare the List pointer to NIL; our list code goes out of its way to ensure that that is the only representation of an empty list. (An acceptable alternative is a plain boolean test for non-null pointer, but explicit mention of NIL is usually preferable.) Various places didn't get that memo and expressed the condition with list_length(), which might not be so bad except that there were such a variety of ways to check it exactly: equal to zero, less than or equal to zero, less than one, yadda yadda. In the name of code readability, let's standardize all those spellings as "list == NIL" or "list != NIL". (There's probably some microscopic efficiency gain too, though few of these look to be at all performance-critical.) A very small number of cases were left as-is because they seemed more consistent with other adjacent list_length tests that way. Peter Smith, with bikeshedding from a number of us Discussion: https://postgr.es/m/CAHut+PtQYe+ENX5KrONMfugf0q6NHg4hR5dAhqEXEc2eefFeig@mail.gmail.com
2022-08-17 17:12:35 +02:00
build_expressions = (stxexprs != NIL);
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/*
* Check that at least two columns were specified in the statement, or
* that we're building statistics on a single expression.
*/
if ((numcols < 2) && (list_length(stxexprs) != 1))
ereport(ERROR,
(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
errmsg("extended statistics require at least 2 columns")));
/*
* Sort the attnums, which makes detecting duplicates somewhat easier, and
* it does not hurt (it does not matter for the contents, unlike for
* indexes, for example).
*/
qsort(attnums, nattnums, sizeof(int16), compare_int16);
/*
* Check for duplicates in the list of columns. The attnums are sorted so
* just check consecutive elements.
*/
for (i = 1; i < nattnums; i++)
{
if (attnums[i] == attnums[i - 1])
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_COLUMN),
errmsg("duplicate column name in statistics definition")));
}
/*
* Check for duplicate expressions. We do two loops, counting the
* occurrences of each expression. This is O(N^2) but we only allow small
* number of expressions and it's not executed often.
*
* XXX We don't cross-check attributes and expressions, because it does
* not seem worth it. In principle we could check that expressions don't
* contain trivial attribute references like "(a)", but the reasoning is
* similar to why we don't bother with extracting columns from
* expressions. It's either expensive or very easy to defeat for
* determined user, and there's no risk if we allow such statistics (the
* statistics is useless, but harmless).
*/
foreach(cell, stxexprs)
{
Node *expr1 = (Node *) lfirst(cell);
int cnt = 0;
foreach(cell2, stxexprs)
{
Node *expr2 = (Node *) lfirst(cell2);
if (equal(expr1, expr2))
cnt += 1;
}
/* every expression should find at least itself */
Assert(cnt >= 1);
if (cnt > 1)
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_COLUMN),
errmsg("duplicate expression in statistics definition")));
}
/* Form an int2vector representation of the sorted column list */
stxkeys = buildint2vector(attnums, nattnums);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
/* construct the char array of enabled statistic types */
ntypes = 0;
if (build_ndistinct)
types[ntypes++] = CharGetDatum(STATS_EXT_NDISTINCT);
Collect and use multi-column dependency stats Follow on patch in the multi-variate statistics patch series. CREATE STATISTICS s1 WITH (dependencies) ON (a, b) FROM t; ANALYZE; will collect dependency stats on (a, b) and then use the measured dependency in subsequent query planning. Commit 7b504eb282ca2f5104b5c00b4f05a3ef6bb1385b added CREATE STATISTICS with n-distinct coefficients. These are now specified using the mutually exclusive option WITH (ndistinct). Author: Tomas Vondra, David Rowley Reviewed-by: Kyotaro HORIGUCHI, Álvaro Herrera, Dean Rasheed, Robert Haas and many other comments and contributions Discussion: https://postgr.es/m/56f40b20-c464-fad2-ff39-06b668fac47c@2ndquadrant.com
2017-04-06 00:00:42 +02:00
if (build_dependencies)
types[ntypes++] = CharGetDatum(STATS_EXT_DEPENDENCIES);
Add support for multivariate MCV lists Introduce a third extended statistic type, supported by the CREATE STATISTICS command - MCV lists, a generalization of the statistic already built and used for individual columns. Compared to the already supported types (n-distinct coefficients and functional dependencies), MCV lists are more complex, include column values and allow estimation of much wider range of common clauses (equality and inequality conditions, IS NULL, IS NOT NULL etc.). Similarly to the other types, a new pseudo-type (pg_mcv_list) is used. Author: Tomas Vondra Reviewed-by: Dean Rasheed, David Rowley, Mark Dilger, Alvaro Herrera Discussion: https://postgr.es/m/dfdac334-9cf2-2597-fb27-f0fb3753f435@2ndquadrant.com
2019-03-27 18:32:18 +01:00
if (build_mcv)
types[ntypes++] = CharGetDatum(STATS_EXT_MCV);
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
if (build_expressions)
types[ntypes++] = CharGetDatum(STATS_EXT_EXPRESSIONS);
Code review for commands/statscmds.c. Fix machine-dependent sorting of column numbers. (Odd behavior would only materialize for column numbers above 255, but that's certainly legal.) Fix poor choice of SQLSTATE for some errors, and improve error message wording. (Notably, "is not a scalar type" is a totally misleading way to explain "does not have a default btree opclass".) Avoid taking AccessExclusiveLock on the associated relation during DROP STATISTICS. That's neither necessary nor desirable, and it could easily have put us into situations where DROP fails (compare commit 68ea2b7f9). Adjust/improve comments. David Rowley and Tom Lane Discussion: https://postgr.es/m/CAKJS1f-GmCfPvBbAEaM5xoVOaYdVgVN1gicALSoYQ77z-+vLbw@mail.gmail.com
2017-04-24 17:15:15 +02:00
Assert(ntypes > 0 && ntypes <= lengthof(types));
Add construct_array_builtin, deconstruct_array_builtin There were many calls to construct_array() and deconstruct_array() for built-in types, for example, when dealing with system catalog columns. These all hardcoded the type attributes necessary to pass to these functions. To simplify this a bit, add construct_array_builtin(), deconstruct_array_builtin() as wrappers that centralize this hardcoded knowledge. This simplifies many call sites and reduces the amount of hardcoded stuff that is spread around. Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://www.postgresql.org/message-id/flat/2914356f-9e5f-8c59-2995-5997fc48bcba%40enterprisedb.com
2022-07-01 10:51:45 +02:00
stxkind = construct_array_builtin(types, ntypes, CHAROID);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/* convert the expressions (if any) to a text datum */
if (stxexprs != NIL)
{
char *exprsString;
exprsString = nodeToString(stxexprs);
exprsDatum = CStringGetTextDatum(exprsString);
pfree(exprsString);
}
else
exprsDatum = (Datum) 0;
Replace uses of heap_open et al with the corresponding table_* function. Author: Andres Freund Discussion: https://postgr.es/m/20190111000539.xbv7s6w7ilcvm7dp@alap3.anarazel.de
2019-01-21 19:32:19 +01:00
statrel = table_open(StatisticExtRelationId, RowExclusiveLock);
Remove WITH OIDS support, change oid catalog column visibility. Previously tables declared WITH OIDS, including a significant fraction of the catalog tables, stored the oid column not as a normal column, but as part of the tuple header. This special column was not shown by default, which was somewhat odd, as it's often (consider e.g. pg_class.oid) one of the more important parts of a row. Neither pg_dump nor COPY included the contents of the oid column by default. The fact that the oid column was not an ordinary column necessitated a significant amount of special case code to support oid columns. That already was painful for the existing, but upcoming work aiming to make table storage pluggable, would have required expanding and duplicating that "specialness" significantly. WITH OIDS has been deprecated since 2005 (commit ff02d0a05280e0). Remove it. Removing includes: - CREATE TABLE and ALTER TABLE syntax for declaring the table to be WITH OIDS has been removed (WITH (oids[ = true]) will error out) - pg_dump does not support dumping tables declared WITH OIDS and will issue a warning when dumping one (and ignore the oid column). - restoring an pg_dump archive with pg_restore will warn when restoring a table with oid contents (and ignore the oid column) - COPY will refuse to load binary dump that includes oids. - pg_upgrade will error out when encountering tables declared WITH OIDS, they have to be altered to remove the oid column first. - Functionality to access the oid of the last inserted row (like plpgsql's RESULT_OID, spi's SPI_lastoid, ...) has been removed. The syntax for declaring a table WITHOUT OIDS (or WITH (oids = false) for CREATE TABLE) is still supported. While that requires a bit of support code, it seems unnecessary to break applications / dumps that do not use oids, and are explicit about not using them. The biggest user of WITH OID columns was postgres' catalog. This commit changes all 'magic' oid columns to be columns that are normally declared and stored. To reduce unnecessary query breakage all the newly added columns are still named 'oid', even if a table's column naming scheme would indicate 'reloid' or such. This obviously requires adapting a lot code, mostly replacing oid access via HeapTupleGetOid() with access to the underlying Form_pg_*->oid column. The bootstrap process now assigns oids for all oid columns in genbki.pl that do not have an explicit value (starting at the largest oid previously used), only oids assigned later by oids will be above FirstBootstrapObjectId. As the oid column now is a normal column the special bootstrap syntax for oids has been removed. Oids are not automatically assigned during insertion anymore, all backend code explicitly assigns oids with GetNewOidWithIndex(). For the rare case that insertions into the catalog via SQL are called for the new pg_nextoid() function can be used (which only works on catalog tables). The fact that oid columns on system tables are now normal columns means that they will be included in the set of columns expanded by * (i.e. SELECT * FROM pg_class will now include the table's oid, previously it did not). It'd not technically be hard to hide oid column by default, but that'd mean confusing behavior would either have to be carried forward forever, or it'd cause breakage down the line. While it's not unlikely that further adjustments are needed, the scope/invasiveness of the patch makes it worthwhile to get merge this now. It's painful to maintain externally, too complicated to commit after the code code freeze, and a dependency of a number of other patches. Catversion bump, for obvious reasons. Author: Andres Freund, with contributions by John Naylor Discussion: https://postgr.es/m/20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de
2018-11-21 00:36:57 +01:00
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
/*
* Everything seems fine, so let's build the pg_statistic_ext tuple.
*/
memset(values, 0, sizeof(values));
memset(nulls, false, sizeof(nulls));
Remove WITH OIDS support, change oid catalog column visibility. Previously tables declared WITH OIDS, including a significant fraction of the catalog tables, stored the oid column not as a normal column, but as part of the tuple header. This special column was not shown by default, which was somewhat odd, as it's often (consider e.g. pg_class.oid) one of the more important parts of a row. Neither pg_dump nor COPY included the contents of the oid column by default. The fact that the oid column was not an ordinary column necessitated a significant amount of special case code to support oid columns. That already was painful for the existing, but upcoming work aiming to make table storage pluggable, would have required expanding and duplicating that "specialness" significantly. WITH OIDS has been deprecated since 2005 (commit ff02d0a05280e0). Remove it. Removing includes: - CREATE TABLE and ALTER TABLE syntax for declaring the table to be WITH OIDS has been removed (WITH (oids[ = true]) will error out) - pg_dump does not support dumping tables declared WITH OIDS and will issue a warning when dumping one (and ignore the oid column). - restoring an pg_dump archive with pg_restore will warn when restoring a table with oid contents (and ignore the oid column) - COPY will refuse to load binary dump that includes oids. - pg_upgrade will error out when encountering tables declared WITH OIDS, they have to be altered to remove the oid column first. - Functionality to access the oid of the last inserted row (like plpgsql's RESULT_OID, spi's SPI_lastoid, ...) has been removed. The syntax for declaring a table WITHOUT OIDS (or WITH (oids = false) for CREATE TABLE) is still supported. While that requires a bit of support code, it seems unnecessary to break applications / dumps that do not use oids, and are explicit about not using them. The biggest user of WITH OID columns was postgres' catalog. This commit changes all 'magic' oid columns to be columns that are normally declared and stored. To reduce unnecessary query breakage all the newly added columns are still named 'oid', even if a table's column naming scheme would indicate 'reloid' or such. This obviously requires adapting a lot code, mostly replacing oid access via HeapTupleGetOid() with access to the underlying Form_pg_*->oid column. The bootstrap process now assigns oids for all oid columns in genbki.pl that do not have an explicit value (starting at the largest oid previously used), only oids assigned later by oids will be above FirstBootstrapObjectId. As the oid column now is a normal column the special bootstrap syntax for oids has been removed. Oids are not automatically assigned during insertion anymore, all backend code explicitly assigns oids with GetNewOidWithIndex(). For the rare case that insertions into the catalog via SQL are called for the new pg_nextoid() function can be used (which only works on catalog tables). The fact that oid columns on system tables are now normal columns means that they will be included in the set of columns expanded by * (i.e. SELECT * FROM pg_class will now include the table's oid, previously it did not). It'd not technically be hard to hide oid column by default, but that'd mean confusing behavior would either have to be carried forward forever, or it'd cause breakage down the line. While it's not unlikely that further adjustments are needed, the scope/invasiveness of the patch makes it worthwhile to get merge this now. It's painful to maintain externally, too complicated to commit after the code code freeze, and a dependency of a number of other patches. Catversion bump, for obvious reasons. Author: Andres Freund, with contributions by John Naylor Discussion: https://postgr.es/m/20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de
2018-11-21 00:36:57 +01:00
statoid = GetNewOidWithIndex(statrel, StatisticExtOidIndexId,
Anum_pg_statistic_ext_oid);
values[Anum_pg_statistic_ext_oid - 1] = ObjectIdGetDatum(statoid);
Rename columns in new pg_statistic_ext catalog The new catalog reused a column prefix "sta" from pg_statistic, but this is undesirable, so change the catalog to use prefix "stx" instead. Also, rename the column that lists enabled statistic kinds as "stxkind" rather than "enabled". Discussion: https://postgr.es/m/CAKJS1f_2t5jhSN7huYRFH3w3rrHfG2QU7hiUHsu-Vdjd1rYT3w@mail.gmail.com
2017-04-17 23:34:29 +02:00
values[Anum_pg_statistic_ext_stxrelid - 1] = ObjectIdGetDatum(relid);
Fix bogus Name assignment in CreateStatistics Apparently, it doesn't work to use a plain cstring as a Name datum: you may end up having random bytes because of failing to zero the bytes after the terminating \0, as indicated by valgrind. I introduced this bug in 5564c1181548, so backpatch this fix to REL_10_STABLE, like that commit. While at it, fix a slightly misleading comment, pointed out by David Rowley.
2018-03-06 17:17:13 +01:00
values[Anum_pg_statistic_ext_stxname - 1] = NameGetDatum(&stxname);
Rename columns in new pg_statistic_ext catalog The new catalog reused a column prefix "sta" from pg_statistic, but this is undesirable, so change the catalog to use prefix "stx" instead. Also, rename the column that lists enabled statistic kinds as "stxkind" rather than "enabled". Discussion: https://postgr.es/m/CAKJS1f_2t5jhSN7huYRFH3w3rrHfG2QU7hiUHsu-Vdjd1rYT3w@mail.gmail.com
2017-04-17 23:34:29 +02:00
values[Anum_pg_statistic_ext_stxnamespace - 1] = ObjectIdGetDatum(namespaceId);
Change type of pg_statistic_ext.stxstattarget Change from int32 to int16, to match attstattarget (changed in 90189eefc1). Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com> Discussion: https://www.postgresql.org/message-id/flat/d6069765-5971-04d3-c10d-e4f7b2e9c459%40eisentraut.org
2023-07-03 07:09:22 +02:00
values[Anum_pg_statistic_ext_stxstattarget - 1] = Int16GetDatum(-1);
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
values[Anum_pg_statistic_ext_stxowner - 1] = ObjectIdGetDatum(stxowner);
Rename columns in new pg_statistic_ext catalog The new catalog reused a column prefix "sta" from pg_statistic, but this is undesirable, so change the catalog to use prefix "stx" instead. Also, rename the column that lists enabled statistic kinds as "stxkind" rather than "enabled". Discussion: https://postgr.es/m/CAKJS1f_2t5jhSN7huYRFH3w3rrHfG2QU7hiUHsu-Vdjd1rYT3w@mail.gmail.com
2017-04-17 23:34:29 +02:00
values[Anum_pg_statistic_ext_stxkeys - 1] = PointerGetDatum(stxkeys);
values[Anum_pg_statistic_ext_stxkind - 1] = PointerGetDatum(stxkind);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
values[Anum_pg_statistic_ext_stxexprs - 1] = exprsDatum;
if (exprsDatum == (Datum) 0)
nulls[Anum_pg_statistic_ext_stxexprs - 1] = true;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
/* insert it into pg_statistic_ext */
htup = heap_form_tuple(statrel->rd_att, values, nulls);
Remove WITH OIDS support, change oid catalog column visibility. Previously tables declared WITH OIDS, including a significant fraction of the catalog tables, stored the oid column not as a normal column, but as part of the tuple header. This special column was not shown by default, which was somewhat odd, as it's often (consider e.g. pg_class.oid) one of the more important parts of a row. Neither pg_dump nor COPY included the contents of the oid column by default. The fact that the oid column was not an ordinary column necessitated a significant amount of special case code to support oid columns. That already was painful for the existing, but upcoming work aiming to make table storage pluggable, would have required expanding and duplicating that "specialness" significantly. WITH OIDS has been deprecated since 2005 (commit ff02d0a05280e0). Remove it. Removing includes: - CREATE TABLE and ALTER TABLE syntax for declaring the table to be WITH OIDS has been removed (WITH (oids[ = true]) will error out) - pg_dump does not support dumping tables declared WITH OIDS and will issue a warning when dumping one (and ignore the oid column). - restoring an pg_dump archive with pg_restore will warn when restoring a table with oid contents (and ignore the oid column) - COPY will refuse to load binary dump that includes oids. - pg_upgrade will error out when encountering tables declared WITH OIDS, they have to be altered to remove the oid column first. - Functionality to access the oid of the last inserted row (like plpgsql's RESULT_OID, spi's SPI_lastoid, ...) has been removed. The syntax for declaring a table WITHOUT OIDS (or WITH (oids = false) for CREATE TABLE) is still supported. While that requires a bit of support code, it seems unnecessary to break applications / dumps that do not use oids, and are explicit about not using them. The biggest user of WITH OID columns was postgres' catalog. This commit changes all 'magic' oid columns to be columns that are normally declared and stored. To reduce unnecessary query breakage all the newly added columns are still named 'oid', even if a table's column naming scheme would indicate 'reloid' or such. This obviously requires adapting a lot code, mostly replacing oid access via HeapTupleGetOid() with access to the underlying Form_pg_*->oid column. The bootstrap process now assigns oids for all oid columns in genbki.pl that do not have an explicit value (starting at the largest oid previously used), only oids assigned later by oids will be above FirstBootstrapObjectId. As the oid column now is a normal column the special bootstrap syntax for oids has been removed. Oids are not automatically assigned during insertion anymore, all backend code explicitly assigns oids with GetNewOidWithIndex(). For the rare case that insertions into the catalog via SQL are called for the new pg_nextoid() function can be used (which only works on catalog tables). The fact that oid columns on system tables are now normal columns means that they will be included in the set of columns expanded by * (i.e. SELECT * FROM pg_class will now include the table's oid, previously it did not). It'd not technically be hard to hide oid column by default, but that'd mean confusing behavior would either have to be carried forward forever, or it'd cause breakage down the line. While it's not unlikely that further adjustments are needed, the scope/invasiveness of the patch makes it worthwhile to get merge this now. It's painful to maintain externally, too complicated to commit after the code code freeze, and a dependency of a number of other patches. Catversion bump, for obvious reasons. Author: Andres Freund, with contributions by John Naylor Discussion: https://postgr.es/m/20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de
2018-11-21 00:36:57 +01:00
CatalogTupleInsert(statrel, htup);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
heap_freetuple(htup);
Remove WITH OIDS support, change oid catalog column visibility. Previously tables declared WITH OIDS, including a significant fraction of the catalog tables, stored the oid column not as a normal column, but as part of the tuple header. This special column was not shown by default, which was somewhat odd, as it's often (consider e.g. pg_class.oid) one of the more important parts of a row. Neither pg_dump nor COPY included the contents of the oid column by default. The fact that the oid column was not an ordinary column necessitated a significant amount of special case code to support oid columns. That already was painful for the existing, but upcoming work aiming to make table storage pluggable, would have required expanding and duplicating that "specialness" significantly. WITH OIDS has been deprecated since 2005 (commit ff02d0a05280e0). Remove it. Removing includes: - CREATE TABLE and ALTER TABLE syntax for declaring the table to be WITH OIDS has been removed (WITH (oids[ = true]) will error out) - pg_dump does not support dumping tables declared WITH OIDS and will issue a warning when dumping one (and ignore the oid column). - restoring an pg_dump archive with pg_restore will warn when restoring a table with oid contents (and ignore the oid column) - COPY will refuse to load binary dump that includes oids. - pg_upgrade will error out when encountering tables declared WITH OIDS, they have to be altered to remove the oid column first. - Functionality to access the oid of the last inserted row (like plpgsql's RESULT_OID, spi's SPI_lastoid, ...) has been removed. The syntax for declaring a table WITHOUT OIDS (or WITH (oids = false) for CREATE TABLE) is still supported. While that requires a bit of support code, it seems unnecessary to break applications / dumps that do not use oids, and are explicit about not using them. The biggest user of WITH OID columns was postgres' catalog. This commit changes all 'magic' oid columns to be columns that are normally declared and stored. To reduce unnecessary query breakage all the newly added columns are still named 'oid', even if a table's column naming scheme would indicate 'reloid' or such. This obviously requires adapting a lot code, mostly replacing oid access via HeapTupleGetOid() with access to the underlying Form_pg_*->oid column. The bootstrap process now assigns oids for all oid columns in genbki.pl that do not have an explicit value (starting at the largest oid previously used), only oids assigned later by oids will be above FirstBootstrapObjectId. As the oid column now is a normal column the special bootstrap syntax for oids has been removed. Oids are not automatically assigned during insertion anymore, all backend code explicitly assigns oids with GetNewOidWithIndex(). For the rare case that insertions into the catalog via SQL are called for the new pg_nextoid() function can be used (which only works on catalog tables). The fact that oid columns on system tables are now normal columns means that they will be included in the set of columns expanded by * (i.e. SELECT * FROM pg_class will now include the table's oid, previously it did not). It'd not technically be hard to hide oid column by default, but that'd mean confusing behavior would either have to be carried forward forever, or it'd cause breakage down the line. While it's not unlikely that further adjustments are needed, the scope/invasiveness of the patch makes it worthwhile to get merge this now. It's painful to maintain externally, too complicated to commit after the code code freeze, and a dependency of a number of other patches. Catversion bump, for obvious reasons. Author: Andres Freund, with contributions by John Naylor Discussion: https://postgr.es/m/20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de
2018-11-21 00:36:57 +01:00
Tighten up relation kind checks for extended statistics We were accepting creation of extended statistics only for regular tables, but they can usefully be created for foreign tables, partitioned tables, and materialized views, too. Allow those cases. While at it, make sure all the rejected cases throw a consistent error message, and add regression tests for the whole thing. Author: David Rowley, Álvaro Herrera Discussion: https://postgr.es/m/CAKJS1f-BmGo410bh5RSPZUvOO0LhmHL2NYmdrC_Jm8pk_FfyCA@mail.gmail.com
2017-04-17 22:55:17 +02:00
relation_close(statrel, RowExclusiveLock);
Fix use-after-free bug Detected by buildfarm member prion
2017-03-24 19:43:03 +01:00
Rework the pg_statistic_ext catalog Since extended statistic got introduced in PostgreSQL 10, there was a single catalog pg_statistic_ext storing both the definitions and built statistic. That's however problematic when a user is supposed to have access only to the definitions, but not to user data. Consider for example pg_dump on a database with RLS enabled - if the pg_statistic_ext catalog respects RLS (which it should, if it contains user data), pg_dump would not see any records and the result would not define any extended statistics. That would be a surprising behavior. Until now this was not a pressing issue, because the existing types of extended statistic (functional dependencies and ndistinct coefficients) do not include any user data directly. This changed with introduction of MCV lists, which do include most common combinations of values. The easiest way to fix this is to split the pg_statistic_ext catalog into two - one for definitions, one for the built statistic values. The new catalog is called pg_statistic_ext_data, and we're maintaining a 1:1 relationship with the old catalog - either there are matching records in both catalogs, or neither of them. Bumped CATVERSION due to changing system catalog definitions. Author: Dean Rasheed, with improvements by me Reviewed-by: Dean Rasheed, John Naylor Discussion: https://postgr.es/m/CAEZATCUhT9rt7Ui%3DVdx4N%3D%3DVV5XOK5dsXfnGgVOz_JhAicB%3DZA%40mail.gmail.com
2019-06-13 17:19:21 +02:00
/*
Add stxdinherit flag to pg_statistic_ext_data Add pg_statistic_ext_data.stxdinherit flag, so that for each extended statistics definition we can store two versions of data - one for the relation alone, one for the whole inheritance tree. This is analogous to pg_statistic.stainherit, but we failed to include such flag in catalogs for extended statistics, and we had to work around it (see commits 859b3003de, 36c4bc6e72 and 20b9fa308e). This changes the relationship between the two catalogs storing extended statistics objects (pg_statistic_ext and pg_statistic_ext_data). Until now, there was a simple 1:1 mapping - for each definition there was one pg_statistic_ext_data row, and this row was inserted while creating the statistics (and then updated during ANALYZE). With the stxdinherit flag, we don't know how many rows there will be (child relations may be added after the statistics object is defined), so there may be up to two rows. We could make CREATE STATISTICS to always create both rows, but that seems wasteful - without partitioning we only need stxdinherit=false rows, and declaratively partitioned tables need only stxdinherit=true. So we no longer initialize pg_statistic_ext_data in CREATE STATISTICS, and instead make that a responsibility of ANALYZE. Which is what we do for regular statistics too. Patch by me, with extensive improvements and fixes by Justin Pryzby. Author: Tomas Vondra, Justin Pryzby Reviewed-by: Tomas Vondra, Justin Pryzby Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
2022-01-16 13:37:56 +01:00
* We used to create the pg_statistic_ext_data tuple too, but it's not
* clear what value should the stxdinherit flag have (it depends on
* whether the rel is partitioned, contains data, etc.)
Rework the pg_statistic_ext catalog Since extended statistic got introduced in PostgreSQL 10, there was a single catalog pg_statistic_ext storing both the definitions and built statistic. That's however problematic when a user is supposed to have access only to the definitions, but not to user data. Consider for example pg_dump on a database with RLS enabled - if the pg_statistic_ext catalog respects RLS (which it should, if it contains user data), pg_dump would not see any records and the result would not define any extended statistics. That would be a surprising behavior. Until now this was not a pressing issue, because the existing types of extended statistic (functional dependencies and ndistinct coefficients) do not include any user data directly. This changed with introduction of MCV lists, which do include most common combinations of values. The easiest way to fix this is to split the pg_statistic_ext catalog into two - one for definitions, one for the built statistic values. The new catalog is called pg_statistic_ext_data, and we're maintaining a 1:1 relationship with the old catalog - either there are matching records in both catalogs, or neither of them. Bumped CATVERSION due to changing system catalog definitions. Author: Dean Rasheed, with improvements by me Reviewed-by: Dean Rasheed, John Naylor Discussion: https://postgr.es/m/CAEZATCUhT9rt7Ui%3DVdx4N%3D%3DVV5XOK5dsXfnGgVOz_JhAicB%3DZA%40mail.gmail.com
2019-06-13 17:19:21 +02:00
*/
Add missing invocations to object access hooks The following commands have been missing calls to object access hooks InvokeObjectPost{Create|Alter}Hook normally applied to all commands: - ALTER RULE RENAME TO - ALTER USER MAPPING - CREATE ACCESS METHOD - CREATE STATISTICS Thanks also to Robert Haas for the discussion. Author: Mark Dilger Reviewed-by: Álvaro Herrera, Michael Paquier Discussion: https://postgr.es/m/435CD295-F409-44E0-91EC-DF32C7AFCD76@enterprisedb.com
2020-05-23 07:03:04 +02:00
InvokeObjectPostCreateHook(StatisticExtRelationId, statoid, 0);
Fix use-after-free bug Detected by buildfarm member prion
2017-03-24 19:43:03 +01:00
/*
Standardize terminology for pg_statistic_ext entries. Consistently refer to such an entry as a "statistics object", not just "statistics" or "extended statistics". Previously we had a mismash of terms, accompanied by utter confusion as to whether the term was singular or plural. That's not only grating (at least to the ear of a native English speaker) but could be outright misleading, eg in error messages that seemed to be referring to multiple objects where only one could be meant. This commit fixes the code and a lot of comments (though I may have missed a few). I also renamed two new SQL functions, pg_get_statisticsextdef -> pg_get_statisticsobjdef pg_statistic_ext_is_visible -> pg_statistics_obj_is_visible to conform better with this terminology. I have not touched the SGML docs other than fixing those function names; the docs certainly need work but it seems like a separable task. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-14 16:54:47 +02:00
* Invalidate relcache so that others see the new statistics object.
Fix use-after-free bug Detected by buildfarm member prion
2017-03-24 19:43:03 +01:00
*/
CacheInvalidateRelcache(rel);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
relation_close(rel, NoLock);
/*
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
* Add an AUTO dependency on each column used in the stats, so that the
* stats object goes away if any or all of them get dropped.
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
*/
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
ObjectAddressSet(myself, StatisticExtRelationId, statoid);
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/* add dependencies for plain column references */
for (i = 0; i < nattnums; i++)
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
{
ObjectAddressSubSet(parentobject, RelationRelationId, relid, attnums[i]);
recordDependencyOn(&myself, &parentobject, DEPENDENCY_AUTO);
}
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/*
Clarify use of "statistics objects" in the code The code inconsistently used "statistic object" or "statistics" where the correct term, as discussed, is actually "statistics object". This improves the state of the code to be more consistent. While on it, fix an incorrect error message introduced in a4d75c8. This error should never happen, as the code states, but it would be misleading. Author: Justin Pryzby Reviewed-by: Álvaro Herrera, Michael Paquier Discussion: https://postgr.es/m/20210924215827.GS831@telsasoft.com Backpatch-through: 14
2021-09-29 08:29:38 +02:00
* If there are no dependencies on a column, give the statistics object an
* auto dependency on the whole table. In most cases, this will be
* redundant, but it might not be if the statistics expressions contain no
* Vars (which might seem strange but possible). This is consistent with
* what we do for indexes in index_create.
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
*
* XXX We intentionally don't consider the expressions before adding this
* dependency, because recordDependencyOnSingleRelExpr may not create any
* dependencies for whole-row Vars.
*/
if (!nattnums)
{
ObjectAddressSet(parentobject, RelationRelationId, relid);
recordDependencyOn(&myself, &parentobject, DEPENDENCY_AUTO);
}
/*
* Store dependencies on anything mentioned in statistics expressions,
* just like we do for index expressions.
*/
if (stxexprs)
recordDependencyOnSingleRelExpr(&myself,
(Node *) stxexprs,
relid,
DEPENDENCY_NORMAL,
Revert per-index collation version tracking feature. Design problems were discovered in the handling of composite types and record types that would cause some relevant versions not to be recorded. Misgivings were also expressed about the use of the pg_depend catalog for this purpose. We're out of time for this release so we'll revert and try again. Commits reverted: 1bf946bd: Doc: Document known problem with Windows collation versions. cf002008: Remove no-longer-relevant test case. ef387bed: Fix bogus collation-version-recording logic. 0fb0a050: Hide internal error for pg_collation_actual_version(<bad OID>). ff942057: Suppress "warning: variable 'collcollate' set but not used". d50e3b1f: Fix assertion in collation version lookup. f24b1569: Rethink extraction of collation dependencies. 257836a7: Track collation versions for indexes. cd6f479e: Add pg_depend.refobjversion. 7d1297df: Remove pg_collation.collversion. Discussion: https://postgr.es/m/CA%2BhUKGLhj5t1fcjqAu8iD9B3ixJtsTNqyCCD4V0aTO9kAKAjjA%40mail.gmail.com
2021-05-07 10:17:42 +02:00
DEPENDENCY_AUTO, false);
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
/*
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
* Also add dependencies on namespace and owner. These are required
* because the stats object might have a different namespace and/or owner
* than the underlying table(s).
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
*/
ObjectAddressSet(parentobject, NamespaceRelationId, namespaceId);
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
recordDependencyOn(&myself, &parentobject, DEPENDENCY_NORMAL);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
recordDependencyOnOwner(StatisticExtRelationId, statoid, stxowner);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
/*
* XXX probably there should be a recordDependencyOnCurrentExtension call
* here too, but we'd have to add support for ALTER EXTENSION ADD/DROP
* STATISTICS, which is more work than it seems worth.
*/
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
/* Add any requested comment */
if (stmt->stxcomment != NULL)
CreateComments(statoid, StatisticExtRelationId, 0,
stmt->stxcomment);
Fix dependencies for extended statistics objects. A stats object ought to have a dependency on each individual column it reads, not the entire table. Doing this honestly lets us get rid of the hard-wired logic in RemoveStatisticsExt, which seems to have been misguidedly modeled on RemoveStatistics; and it will be far easier to extend to multiple tables later. Also, add overlooked dependency on owner, and make the dependency on schema be NORMAL like every other such dependency. There remains some unfinished work here, which is to allow statistics objects to be extension members. That takes more effort than just adding the dependency call, though, so I left it out for now. initdb forced because this changes the set of pg_depend records that should exist for a statistics object. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-12 22:26:31 +02:00
/* Return stats object's address */
return myself;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
}
Allow setting statistics target for extended statistics When building statistics, we need to decide how many rows to sample and how accurate the resulting statistics should be. Until now, it was not possible to explicitly define statistics target for extended statistics objects, the value was always computed from the per-attribute targets with a fallback to the system-wide default statistics target. That's a bit inconvenient, as it ties together the statistics target set for per-column and extended statistics. In some cases it may be useful to require larger sample / higher accuracy for extended statics (or the other way around), but with this approach that's not possible. So this commit introduces a new command, allowing to specify statistics target for individual extended statistics objects, overriding the value derived from per-attribute targets (and the system default). ALTER STATISTICS stat_name SET STATISTICS target_value; When determining statistics target for an extended statistics object we first look at this explicitly set value. When this value is -1, we fall back to the old formula, looking at the per-attribute targets first and then the system default. This means the behavior is backwards compatible with older PostgreSQL releases. Author: Tomas Vondra Discussion: https://postgr.es/m/20190618213357.vli3i23vpkset2xd@development Reviewed-by: Kirk Jamison, Dean Rasheed
2019-09-10 20:09:27 +02:00
/*
* ALTER STATISTICS
*/
ObjectAddress
AlterStatistics(AlterStatsStmt *stmt)
{
Relation rel;
Oid stxoid;
HeapTuple oldtup;
HeapTuple newtup;
Datum repl_val[Natts_pg_statistic_ext];
bool repl_null[Natts_pg_statistic_ext];
bool repl_repl[Natts_pg_statistic_ext];
ObjectAddress address;
int newtarget = stmt->stxstattarget;
/* Limit statistics target to a sane range */
if (newtarget < -1)
{
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("statistics target %d is too low",
newtarget)));
}
Add macro for maximum statistics target The number of places where 10000 was hardcoded had grown a bit beyond the comfort level. Introduce a macro MAX_STATISTICS_TARGET instead. Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com> Discussion: https://www.postgresql.org/message-id/flat/d6069765-5971-04d3-c10d-e4f7b2e9c459%40eisentraut.org
2023-07-03 07:09:22 +02:00
else if (newtarget > MAX_STATISTICS_TARGET)
Allow setting statistics target for extended statistics When building statistics, we need to decide how many rows to sample and how accurate the resulting statistics should be. Until now, it was not possible to explicitly define statistics target for extended statistics objects, the value was always computed from the per-attribute targets with a fallback to the system-wide default statistics target. That's a bit inconvenient, as it ties together the statistics target set for per-column and extended statistics. In some cases it may be useful to require larger sample / higher accuracy for extended statics (or the other way around), but with this approach that's not possible. So this commit introduces a new command, allowing to specify statistics target for individual extended statistics objects, overriding the value derived from per-attribute targets (and the system default). ALTER STATISTICS stat_name SET STATISTICS target_value; When determining statistics target for an extended statistics object we first look at this explicitly set value. When this value is -1, we fall back to the old formula, looking at the per-attribute targets first and then the system default. This means the behavior is backwards compatible with older PostgreSQL releases. Author: Tomas Vondra Discussion: https://postgr.es/m/20190618213357.vli3i23vpkset2xd@development Reviewed-by: Kirk Jamison, Dean Rasheed
2019-09-10 20:09:27 +02:00
{
Add macro for maximum statistics target The number of places where 10000 was hardcoded had grown a bit beyond the comfort level. Introduce a macro MAX_STATISTICS_TARGET instead. Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com> Discussion: https://www.postgresql.org/message-id/flat/d6069765-5971-04d3-c10d-e4f7b2e9c459%40eisentraut.org
2023-07-03 07:09:22 +02:00
newtarget = MAX_STATISTICS_TARGET;
Allow setting statistics target for extended statistics When building statistics, we need to decide how many rows to sample and how accurate the resulting statistics should be. Until now, it was not possible to explicitly define statistics target for extended statistics objects, the value was always computed from the per-attribute targets with a fallback to the system-wide default statistics target. That's a bit inconvenient, as it ties together the statistics target set for per-column and extended statistics. In some cases it may be useful to require larger sample / higher accuracy for extended statics (or the other way around), but with this approach that's not possible. So this commit introduces a new command, allowing to specify statistics target for individual extended statistics objects, overriding the value derived from per-attribute targets (and the system default). ALTER STATISTICS stat_name SET STATISTICS target_value; When determining statistics target for an extended statistics object we first look at this explicitly set value. When this value is -1, we fall back to the old formula, looking at the per-attribute targets first and then the system default. This means the behavior is backwards compatible with older PostgreSQL releases. Author: Tomas Vondra Discussion: https://postgr.es/m/20190618213357.vli3i23vpkset2xd@development Reviewed-by: Kirk Jamison, Dean Rasheed
2019-09-10 20:09:27 +02:00
ereport(WARNING,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("lowering statistics target to %d",
newtarget)));
}
/* lookup OID of the statistics object */
stxoid = get_statistics_object_oid(stmt->defnames, stmt->missing_ok);
/*
Clarify use of "statistics objects" in the code The code inconsistently used "statistic object" or "statistics" where the correct term, as discussed, is actually "statistics object". This improves the state of the code to be more consistent. While on it, fix an incorrect error message introduced in a4d75c8. This error should never happen, as the code states, but it would be misleading. Author: Justin Pryzby Reviewed-by: Álvaro Herrera, Michael Paquier Discussion: https://postgr.es/m/20210924215827.GS831@telsasoft.com Backpatch-through: 14
2021-09-29 08:29:38 +02:00
* If we got here and the OID is not valid, it means the statistics object
* does not exist, but the command specified IF EXISTS. So report this as
* a simple NOTICE and we're done.
Allow setting statistics target for extended statistics When building statistics, we need to decide how many rows to sample and how accurate the resulting statistics should be. Until now, it was not possible to explicitly define statistics target for extended statistics objects, the value was always computed from the per-attribute targets with a fallback to the system-wide default statistics target. That's a bit inconvenient, as it ties together the statistics target set for per-column and extended statistics. In some cases it may be useful to require larger sample / higher accuracy for extended statics (or the other way around), but with this approach that's not possible. So this commit introduces a new command, allowing to specify statistics target for individual extended statistics objects, overriding the value derived from per-attribute targets (and the system default). ALTER STATISTICS stat_name SET STATISTICS target_value; When determining statistics target for an extended statistics object we first look at this explicitly set value. When this value is -1, we fall back to the old formula, looking at the per-attribute targets first and then the system default. This means the behavior is backwards compatible with older PostgreSQL releases. Author: Tomas Vondra Discussion: https://postgr.es/m/20190618213357.vli3i23vpkset2xd@development Reviewed-by: Kirk Jamison, Dean Rasheed
2019-09-10 20:09:27 +02:00
*/
if (!OidIsValid(stxoid))
{
char *schemaname;
char *statname;
Assert(stmt->missing_ok);
DeconstructQualifiedName(stmt->defnames, &schemaname, &statname);
if (schemaname)
ereport(NOTICE,
(errmsg("statistics object \"%s.%s\" does not exist, skipping",
schemaname, statname)));
else
ereport(NOTICE,
(errmsg("statistics object \"%s\" does not exist, skipping",
statname)));
return InvalidObjectAddress;
}
/* Search pg_statistic_ext */
rel = table_open(StatisticExtRelationId, RowExclusiveLock);
oldtup = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxoid));
Check syscache result in AlterStatistics The syscache lookup may return NULL even for valid OID, for example due to a concurrent DROP STATISTICS, so a HeapTupleIsValid is necessary. Without it, it may fail with a segfault. Reported by Alexander Lakhin, patch by me. Backpatch to 13, where ALTER STATISTICS ... SET STATISTICS was introduced. Backpatch-through: 13 Discussion: https://postgr.es/m/17372-bf3b6e947e35ae77%40postgresql.org
2022-01-23 02:49:41 +01:00
if (!HeapTupleIsValid(oldtup))
elog(ERROR, "cache lookup failed for extended statistics object %u", stxoid);
Allow setting statistics target for extended statistics When building statistics, we need to decide how many rows to sample and how accurate the resulting statistics should be. Until now, it was not possible to explicitly define statistics target for extended statistics objects, the value was always computed from the per-attribute targets with a fallback to the system-wide default statistics target. That's a bit inconvenient, as it ties together the statistics target set for per-column and extended statistics. In some cases it may be useful to require larger sample / higher accuracy for extended statics (or the other way around), but with this approach that's not possible. So this commit introduces a new command, allowing to specify statistics target for individual extended statistics objects, overriding the value derived from per-attribute targets (and the system default). ALTER STATISTICS stat_name SET STATISTICS target_value; When determining statistics target for an extended statistics object we first look at this explicitly set value. When this value is -1, we fall back to the old formula, looking at the per-attribute targets first and then the system default. This means the behavior is backwards compatible with older PostgreSQL releases. Author: Tomas Vondra Discussion: https://postgr.es/m/20190618213357.vli3i23vpkset2xd@development Reviewed-by: Kirk Jamison, Dean Rasheed
2019-09-10 20:09:27 +02:00
/* Must be owner of the existing statistics object */
Refactor ownercheck functions Instead of dozens of mostly-duplicate pg_foo_ownercheck() functions, write one common function object_ownercheck() that can handle almost all of them. We already have all the information we need, such as which system catalog corresponds to which catalog table and which column is the owner column. Reviewed-by: Corey Huinker <corey.huinker@gmail.com> Reviewed-by: Antonin Houska <ah@cybertec.at> Discussion: https://www.postgresql.org/message-id/flat/95c30f96-4060-2f48-98b5-a4392d3b6066@enterprisedb.com
2022-11-13 08:11:17 +01:00
if (!object_ownercheck(StatisticExtRelationId, stxoid, GetUserId()))
Allow setting statistics target for extended statistics When building statistics, we need to decide how many rows to sample and how accurate the resulting statistics should be. Until now, it was not possible to explicitly define statistics target for extended statistics objects, the value was always computed from the per-attribute targets with a fallback to the system-wide default statistics target. That's a bit inconvenient, as it ties together the statistics target set for per-column and extended statistics. In some cases it may be useful to require larger sample / higher accuracy for extended statics (or the other way around), but with this approach that's not possible. So this commit introduces a new command, allowing to specify statistics target for individual extended statistics objects, overriding the value derived from per-attribute targets (and the system default). ALTER STATISTICS stat_name SET STATISTICS target_value; When determining statistics target for an extended statistics object we first look at this explicitly set value. When this value is -1, we fall back to the old formula, looking at the per-attribute targets first and then the system default. This means the behavior is backwards compatible with older PostgreSQL releases. Author: Tomas Vondra Discussion: https://postgr.es/m/20190618213357.vli3i23vpkset2xd@development Reviewed-by: Kirk Jamison, Dean Rasheed
2019-09-10 20:09:27 +02:00
aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_STATISTIC_EXT,
NameListToString(stmt->defnames));
/* Build new tuple. */
memset(repl_val, 0, sizeof(repl_val));
memset(repl_null, false, sizeof(repl_null));
memset(repl_repl, false, sizeof(repl_repl));
/* replace the stxstattarget column */
repl_repl[Anum_pg_statistic_ext_stxstattarget - 1] = true;
Change type of pg_statistic_ext.stxstattarget Change from int32 to int16, to match attstattarget (changed in 90189eefc1). Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com> Discussion: https://www.postgresql.org/message-id/flat/d6069765-5971-04d3-c10d-e4f7b2e9c459%40eisentraut.org
2023-07-03 07:09:22 +02:00
repl_val[Anum_pg_statistic_ext_stxstattarget - 1] = Int16GetDatum(newtarget);
Allow setting statistics target for extended statistics When building statistics, we need to decide how many rows to sample and how accurate the resulting statistics should be. Until now, it was not possible to explicitly define statistics target for extended statistics objects, the value was always computed from the per-attribute targets with a fallback to the system-wide default statistics target. That's a bit inconvenient, as it ties together the statistics target set for per-column and extended statistics. In some cases it may be useful to require larger sample / higher accuracy for extended statics (or the other way around), but with this approach that's not possible. So this commit introduces a new command, allowing to specify statistics target for individual extended statistics objects, overriding the value derived from per-attribute targets (and the system default). ALTER STATISTICS stat_name SET STATISTICS target_value; When determining statistics target for an extended statistics object we first look at this explicitly set value. When this value is -1, we fall back to the old formula, looking at the per-attribute targets first and then the system default. This means the behavior is backwards compatible with older PostgreSQL releases. Author: Tomas Vondra Discussion: https://postgr.es/m/20190618213357.vli3i23vpkset2xd@development Reviewed-by: Kirk Jamison, Dean Rasheed
2019-09-10 20:09:27 +02:00
newtup = heap_modify_tuple(oldtup, RelationGetDescr(rel),
repl_val, repl_null, repl_repl);
/* Update system catalog. */
CatalogTupleUpdate(rel, &newtup->t_self, newtup);
InvokeObjectPostAlterHook(StatisticExtRelationId, stxoid, 0);
ObjectAddressSet(address, StatisticExtRelationId, stxoid);
/*
* NOTE: because we only support altering the statistics target, not the
* other fields, there is no need to update dependencies.
*/
heap_freetuple(newtup);
ReleaseSysCache(oldtup);
table_close(rel, RowExclusiveLock);
return address;
}
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
/*
Add stxdinherit flag to pg_statistic_ext_data Add pg_statistic_ext_data.stxdinherit flag, so that for each extended statistics definition we can store two versions of data - one for the relation alone, one for the whole inheritance tree. This is analogous to pg_statistic.stainherit, but we failed to include such flag in catalogs for extended statistics, and we had to work around it (see commits 859b3003de, 36c4bc6e72 and 20b9fa308e). This changes the relationship between the two catalogs storing extended statistics objects (pg_statistic_ext and pg_statistic_ext_data). Until now, there was a simple 1:1 mapping - for each definition there was one pg_statistic_ext_data row, and this row was inserted while creating the statistics (and then updated during ANALYZE). With the stxdinherit flag, we don't know how many rows there will be (child relations may be added after the statistics object is defined), so there may be up to two rows. We could make CREATE STATISTICS to always create both rows, but that seems wasteful - without partitioning we only need stxdinherit=false rows, and declaratively partitioned tables need only stxdinherit=true. So we no longer initialize pg_statistic_ext_data in CREATE STATISTICS, and instead make that a responsibility of ANALYZE. Which is what we do for regular statistics too. Patch by me, with extensive improvements and fixes by Justin Pryzby. Author: Tomas Vondra, Justin Pryzby Reviewed-by: Tomas Vondra, Justin Pryzby Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
2022-01-16 13:37:56 +01:00
* Delete entry in pg_statistic_ext_data catalog. We don't know if the row
* exists, so don't error out.
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
*/
void
Add stxdinherit flag to pg_statistic_ext_data Add pg_statistic_ext_data.stxdinherit flag, so that for each extended statistics definition we can store two versions of data - one for the relation alone, one for the whole inheritance tree. This is analogous to pg_statistic.stainherit, but we failed to include such flag in catalogs for extended statistics, and we had to work around it (see commits 859b3003de, 36c4bc6e72 and 20b9fa308e). This changes the relationship between the two catalogs storing extended statistics objects (pg_statistic_ext and pg_statistic_ext_data). Until now, there was a simple 1:1 mapping - for each definition there was one pg_statistic_ext_data row, and this row was inserted while creating the statistics (and then updated during ANALYZE). With the stxdinherit flag, we don't know how many rows there will be (child relations may be added after the statistics object is defined), so there may be up to two rows. We could make CREATE STATISTICS to always create both rows, but that seems wasteful - without partitioning we only need stxdinherit=false rows, and declaratively partitioned tables need only stxdinherit=true. So we no longer initialize pg_statistic_ext_data in CREATE STATISTICS, and instead make that a responsibility of ANALYZE. Which is what we do for regular statistics too. Patch by me, with extensive improvements and fixes by Justin Pryzby. Author: Tomas Vondra, Justin Pryzby Reviewed-by: Tomas Vondra, Justin Pryzby Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
2022-01-16 13:37:56 +01:00
RemoveStatisticsDataById(Oid statsOid, bool inh)
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
{
Relation relation;
HeapTuple tup;
Rework the pg_statistic_ext catalog Since extended statistic got introduced in PostgreSQL 10, there was a single catalog pg_statistic_ext storing both the definitions and built statistic. That's however problematic when a user is supposed to have access only to the definitions, but not to user data. Consider for example pg_dump on a database with RLS enabled - if the pg_statistic_ext catalog respects RLS (which it should, if it contains user data), pg_dump would not see any records and the result would not define any extended statistics. That would be a surprising behavior. Until now this was not a pressing issue, because the existing types of extended statistic (functional dependencies and ndistinct coefficients) do not include any user data directly. This changed with introduction of MCV lists, which do include most common combinations of values. The easiest way to fix this is to split the pg_statistic_ext catalog into two - one for definitions, one for the built statistic values. The new catalog is called pg_statistic_ext_data, and we're maintaining a 1:1 relationship with the old catalog - either there are matching records in both catalogs, or neither of them. Bumped CATVERSION due to changing system catalog definitions. Author: Dean Rasheed, with improvements by me Reviewed-by: Dean Rasheed, John Naylor Discussion: https://postgr.es/m/CAEZATCUhT9rt7Ui%3DVdx4N%3D%3DVV5XOK5dsXfnGgVOz_JhAicB%3DZA%40mail.gmail.com
2019-06-13 17:19:21 +02:00
relation = table_open(StatisticExtDataRelationId, RowExclusiveLock);
Add stxdinherit flag to pg_statistic_ext_data Add pg_statistic_ext_data.stxdinherit flag, so that for each extended statistics definition we can store two versions of data - one for the relation alone, one for the whole inheritance tree. This is analogous to pg_statistic.stainherit, but we failed to include such flag in catalogs for extended statistics, and we had to work around it (see commits 859b3003de, 36c4bc6e72 and 20b9fa308e). This changes the relationship between the two catalogs storing extended statistics objects (pg_statistic_ext and pg_statistic_ext_data). Until now, there was a simple 1:1 mapping - for each definition there was one pg_statistic_ext_data row, and this row was inserted while creating the statistics (and then updated during ANALYZE). With the stxdinherit flag, we don't know how many rows there will be (child relations may be added after the statistics object is defined), so there may be up to two rows. We could make CREATE STATISTICS to always create both rows, but that seems wasteful - without partitioning we only need stxdinherit=false rows, and declaratively partitioned tables need only stxdinherit=true. So we no longer initialize pg_statistic_ext_data in CREATE STATISTICS, and instead make that a responsibility of ANALYZE. Which is what we do for regular statistics too. Patch by me, with extensive improvements and fixes by Justin Pryzby. Author: Tomas Vondra, Justin Pryzby Reviewed-by: Tomas Vondra, Justin Pryzby Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
2022-01-16 13:37:56 +01:00
tup = SearchSysCache2(STATEXTDATASTXOID, ObjectIdGetDatum(statsOid),
BoolGetDatum(inh));
Rework the pg_statistic_ext catalog Since extended statistic got introduced in PostgreSQL 10, there was a single catalog pg_statistic_ext storing both the definitions and built statistic. That's however problematic when a user is supposed to have access only to the definitions, but not to user data. Consider for example pg_dump on a database with RLS enabled - if the pg_statistic_ext catalog respects RLS (which it should, if it contains user data), pg_dump would not see any records and the result would not define any extended statistics. That would be a surprising behavior. Until now this was not a pressing issue, because the existing types of extended statistic (functional dependencies and ndistinct coefficients) do not include any user data directly. This changed with introduction of MCV lists, which do include most common combinations of values. The easiest way to fix this is to split the pg_statistic_ext catalog into two - one for definitions, one for the built statistic values. The new catalog is called pg_statistic_ext_data, and we're maintaining a 1:1 relationship with the old catalog - either there are matching records in both catalogs, or neither of them. Bumped CATVERSION due to changing system catalog definitions. Author: Dean Rasheed, with improvements by me Reviewed-by: Dean Rasheed, John Naylor Discussion: https://postgr.es/m/CAEZATCUhT9rt7Ui%3DVdx4N%3D%3DVV5XOK5dsXfnGgVOz_JhAicB%3DZA%40mail.gmail.com
2019-06-13 17:19:21 +02:00
Add stxdinherit flag to pg_statistic_ext_data Add pg_statistic_ext_data.stxdinherit flag, so that for each extended statistics definition we can store two versions of data - one for the relation alone, one for the whole inheritance tree. This is analogous to pg_statistic.stainherit, but we failed to include such flag in catalogs for extended statistics, and we had to work around it (see commits 859b3003de, 36c4bc6e72 and 20b9fa308e). This changes the relationship between the two catalogs storing extended statistics objects (pg_statistic_ext and pg_statistic_ext_data). Until now, there was a simple 1:1 mapping - for each definition there was one pg_statistic_ext_data row, and this row was inserted while creating the statistics (and then updated during ANALYZE). With the stxdinherit flag, we don't know how many rows there will be (child relations may be added after the statistics object is defined), so there may be up to two rows. We could make CREATE STATISTICS to always create both rows, but that seems wasteful - without partitioning we only need stxdinherit=false rows, and declaratively partitioned tables need only stxdinherit=true. So we no longer initialize pg_statistic_ext_data in CREATE STATISTICS, and instead make that a responsibility of ANALYZE. Which is what we do for regular statistics too. Patch by me, with extensive improvements and fixes by Justin Pryzby. Author: Tomas Vondra, Justin Pryzby Reviewed-by: Tomas Vondra, Justin Pryzby Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
2022-01-16 13:37:56 +01:00
/* We don't know if the data row for inh value exists. */
if (HeapTupleIsValid(tup))
{
CatalogTupleDelete(relation, &tup->t_self);
Rework the pg_statistic_ext catalog Since extended statistic got introduced in PostgreSQL 10, there was a single catalog pg_statistic_ext storing both the definitions and built statistic. That's however problematic when a user is supposed to have access only to the definitions, but not to user data. Consider for example pg_dump on a database with RLS enabled - if the pg_statistic_ext catalog respects RLS (which it should, if it contains user data), pg_dump would not see any records and the result would not define any extended statistics. That would be a surprising behavior. Until now this was not a pressing issue, because the existing types of extended statistic (functional dependencies and ndistinct coefficients) do not include any user data directly. This changed with introduction of MCV lists, which do include most common combinations of values. The easiest way to fix this is to split the pg_statistic_ext catalog into two - one for definitions, one for the built statistic values. The new catalog is called pg_statistic_ext_data, and we're maintaining a 1:1 relationship with the old catalog - either there are matching records in both catalogs, or neither of them. Bumped CATVERSION due to changing system catalog definitions. Author: Dean Rasheed, with improvements by me Reviewed-by: Dean Rasheed, John Naylor Discussion: https://postgr.es/m/CAEZATCUhT9rt7Ui%3DVdx4N%3D%3DVV5XOK5dsXfnGgVOz_JhAicB%3DZA%40mail.gmail.com
2019-06-13 17:19:21 +02:00
Add stxdinherit flag to pg_statistic_ext_data Add pg_statistic_ext_data.stxdinherit flag, so that for each extended statistics definition we can store two versions of data - one for the relation alone, one for the whole inheritance tree. This is analogous to pg_statistic.stainherit, but we failed to include such flag in catalogs for extended statistics, and we had to work around it (see commits 859b3003de, 36c4bc6e72 and 20b9fa308e). This changes the relationship between the two catalogs storing extended statistics objects (pg_statistic_ext and pg_statistic_ext_data). Until now, there was a simple 1:1 mapping - for each definition there was one pg_statistic_ext_data row, and this row was inserted while creating the statistics (and then updated during ANALYZE). With the stxdinherit flag, we don't know how many rows there will be (child relations may be added after the statistics object is defined), so there may be up to two rows. We could make CREATE STATISTICS to always create both rows, but that seems wasteful - without partitioning we only need stxdinherit=false rows, and declaratively partitioned tables need only stxdinherit=true. So we no longer initialize pg_statistic_ext_data in CREATE STATISTICS, and instead make that a responsibility of ANALYZE. Which is what we do for regular statistics too. Patch by me, with extensive improvements and fixes by Justin Pryzby. Author: Tomas Vondra, Justin Pryzby Reviewed-by: Tomas Vondra, Justin Pryzby Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
2022-01-16 13:37:56 +01:00
ReleaseSysCache(tup);
}
Rework the pg_statistic_ext catalog Since extended statistic got introduced in PostgreSQL 10, there was a single catalog pg_statistic_ext storing both the definitions and built statistic. That's however problematic when a user is supposed to have access only to the definitions, but not to user data. Consider for example pg_dump on a database with RLS enabled - if the pg_statistic_ext catalog respects RLS (which it should, if it contains user data), pg_dump would not see any records and the result would not define any extended statistics. That would be a surprising behavior. Until now this was not a pressing issue, because the existing types of extended statistic (functional dependencies and ndistinct coefficients) do not include any user data directly. This changed with introduction of MCV lists, which do include most common combinations of values. The easiest way to fix this is to split the pg_statistic_ext catalog into two - one for definitions, one for the built statistic values. The new catalog is called pg_statistic_ext_data, and we're maintaining a 1:1 relationship with the old catalog - either there are matching records in both catalogs, or neither of them. Bumped CATVERSION due to changing system catalog definitions. Author: Dean Rasheed, with improvements by me Reviewed-by: Dean Rasheed, John Naylor Discussion: https://postgr.es/m/CAEZATCUhT9rt7Ui%3DVdx4N%3D%3DVV5XOK5dsXfnGgVOz_JhAicB%3DZA%40mail.gmail.com
2019-06-13 17:19:21 +02:00
table_close(relation, RowExclusiveLock);
Add stxdinherit flag to pg_statistic_ext_data Add pg_statistic_ext_data.stxdinherit flag, so that for each extended statistics definition we can store two versions of data - one for the relation alone, one for the whole inheritance tree. This is analogous to pg_statistic.stainherit, but we failed to include such flag in catalogs for extended statistics, and we had to work around it (see commits 859b3003de, 36c4bc6e72 and 20b9fa308e). This changes the relationship between the two catalogs storing extended statistics objects (pg_statistic_ext and pg_statistic_ext_data). Until now, there was a simple 1:1 mapping - for each definition there was one pg_statistic_ext_data row, and this row was inserted while creating the statistics (and then updated during ANALYZE). With the stxdinherit flag, we don't know how many rows there will be (child relations may be added after the statistics object is defined), so there may be up to two rows. We could make CREATE STATISTICS to always create both rows, but that seems wasteful - without partitioning we only need stxdinherit=false rows, and declaratively partitioned tables need only stxdinherit=true. So we no longer initialize pg_statistic_ext_data in CREATE STATISTICS, and instead make that a responsibility of ANALYZE. Which is what we do for regular statistics too. Patch by me, with extensive improvements and fixes by Justin Pryzby. Author: Tomas Vondra, Justin Pryzby Reviewed-by: Tomas Vondra, Justin Pryzby Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
2022-01-16 13:37:56 +01:00
}
/*
* Guts of statistics object deletion.
*/
void
RemoveStatisticsById(Oid statsOid)
{
Relation relation;
Lock table in DROP STATISTICS The DROP STATISTICS code failed to properly lock the table, leading to ERROR: tuple concurrently deleted when executed concurrently with ANALYZE. Fixed by modifying RemoveStatisticsById() to acquire the same lock as ANALYZE. This function is called only by DROP STATISTICS, as ANALYZE calls RemoveStatisticsDataById() directly. Reported by Justin Pryzby, fix by me. Backpatch through 12. The code was like this since it was introduced in 10, but older releases are EOL. Reported-by: Justin Pryzby Reviewed-by: Tom Lane Backpatch-through: 12 Discussion: https://postgr.es/m/ZUuk-8CfbYeq6g_u@pryzbyj2023
2023-11-19 21:03:29 +01:00
Relation rel;
Add stxdinherit flag to pg_statistic_ext_data Add pg_statistic_ext_data.stxdinherit flag, so that for each extended statistics definition we can store two versions of data - one for the relation alone, one for the whole inheritance tree. This is analogous to pg_statistic.stainherit, but we failed to include such flag in catalogs for extended statistics, and we had to work around it (see commits 859b3003de, 36c4bc6e72 and 20b9fa308e). This changes the relationship between the two catalogs storing extended statistics objects (pg_statistic_ext and pg_statistic_ext_data). Until now, there was a simple 1:1 mapping - for each definition there was one pg_statistic_ext_data row, and this row was inserted while creating the statistics (and then updated during ANALYZE). With the stxdinherit flag, we don't know how many rows there will be (child relations may be added after the statistics object is defined), so there may be up to two rows. We could make CREATE STATISTICS to always create both rows, but that seems wasteful - without partitioning we only need stxdinherit=false rows, and declaratively partitioned tables need only stxdinherit=true. So we no longer initialize pg_statistic_ext_data in CREATE STATISTICS, and instead make that a responsibility of ANALYZE. Which is what we do for regular statistics too. Patch by me, with extensive improvements and fixes by Justin Pryzby. Author: Tomas Vondra, Justin Pryzby Reviewed-by: Tomas Vondra, Justin Pryzby Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
2022-01-16 13:37:56 +01:00
HeapTuple tup;
Form_pg_statistic_ext statext;
Oid relid;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
/*
Code review for commands/statscmds.c. Fix machine-dependent sorting of column numbers. (Odd behavior would only materialize for column numbers above 255, but that's certainly legal.) Fix poor choice of SQLSTATE for some errors, and improve error message wording. (Notably, "is not a scalar type" is a totally misleading way to explain "does not have a default btree opclass".) Avoid taking AccessExclusiveLock on the associated relation during DROP STATISTICS. That's neither necessary nor desirable, and it could easily have put us into situations where DROP fails (compare commit 68ea2b7f9). Adjust/improve comments. David Rowley and Tom Lane Discussion: https://postgr.es/m/CAKJS1f-GmCfPvBbAEaM5xoVOaYdVgVN1gicALSoYQ77z-+vLbw@mail.gmail.com
2017-04-24 17:15:15 +02:00
* Delete the pg_statistic_ext tuple. Also send out a cache inval on the
* associated table, so that dependent plans will be rebuilt.
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
*/
Replace uses of heap_open et al with the corresponding table_* function. Author: Andres Freund Discussion: https://postgr.es/m/20190111000539.xbv7s6w7ilcvm7dp@alap3.anarazel.de
2019-01-21 19:32:19 +01:00
relation = table_open(StatisticExtRelationId, RowExclusiveLock);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
tup = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(statsOid));
if (!HeapTupleIsValid(tup)) /* should not happen */
Standardize terminology for pg_statistic_ext entries. Consistently refer to such an entry as a "statistics object", not just "statistics" or "extended statistics". Previously we had a mismash of terms, accompanied by utter confusion as to whether the term was singular or plural. That's not only grating (at least to the ear of a native English speaker) but could be outright misleading, eg in error messages that seemed to be referring to multiple objects where only one could be meant. This commit fixes the code and a lot of comments (though I may have missed a few). I also renamed two new SQL functions, pg_get_statisticsextdef -> pg_get_statisticsobjdef pg_statistic_ext_is_visible -> pg_statistics_obj_is_visible to conform better with this terminology. I have not touched the SGML docs other than fixing those function names; the docs certainly need work but it seems like a separable task. Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us
2017-05-14 16:54:47 +02:00
elog(ERROR, "cache lookup failed for statistics object %u", statsOid);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
statext = (Form_pg_statistic_ext) GETSTRUCT(tup);
Rename columns in new pg_statistic_ext catalog The new catalog reused a column prefix "sta" from pg_statistic, but this is undesirable, so change the catalog to use prefix "stx" instead. Also, rename the column that lists enabled statistic kinds as "stxkind" rather than "enabled". Discussion: https://postgr.es/m/CAKJS1f_2t5jhSN7huYRFH3w3rrHfG2QU7hiUHsu-Vdjd1rYT3w@mail.gmail.com
2017-04-17 23:34:29 +02:00
relid = statext->stxrelid;
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Lock table in DROP STATISTICS The DROP STATISTICS code failed to properly lock the table, leading to ERROR: tuple concurrently deleted when executed concurrently with ANALYZE. Fixed by modifying RemoveStatisticsById() to acquire the same lock as ANALYZE. This function is called only by DROP STATISTICS, as ANALYZE calls RemoveStatisticsDataById() directly. Reported by Justin Pryzby, fix by me. Backpatch through 12. The code was like this since it was introduced in 10, but older releases are EOL. Reported-by: Justin Pryzby Reviewed-by: Tom Lane Backpatch-through: 12 Discussion: https://postgr.es/m/ZUuk-8CfbYeq6g_u@pryzbyj2023
2023-11-19 21:03:29 +01:00
/*
* Delete the pg_statistic_ext_data tuples holding the actual statistical
* data. There might be data with/without inheritance, so attempt deleting
* both. We lock the user table first, to prevent other processes (e.g.
* DROP STATISTICS) from removing the row concurrently.
*/
rel = table_open(relid, ShareUpdateExclusiveLock);
RemoveStatisticsDataById(statsOid, true);
RemoveStatisticsDataById(statsOid, false);
Code review for commands/statscmds.c. Fix machine-dependent sorting of column numbers. (Odd behavior would only materialize for column numbers above 255, but that's certainly legal.) Fix poor choice of SQLSTATE for some errors, and improve error message wording. (Notably, "is not a scalar type" is a totally misleading way to explain "does not have a default btree opclass".) Avoid taking AccessExclusiveLock on the associated relation during DROP STATISTICS. That's neither necessary nor desirable, and it could easily have put us into situations where DROP fails (compare commit 68ea2b7f9). Adjust/improve comments. David Rowley and Tom Lane Discussion: https://postgr.es/m/CAKJS1f-GmCfPvBbAEaM5xoVOaYdVgVN1gicALSoYQ77z-+vLbw@mail.gmail.com
2017-04-24 17:15:15 +02:00
CacheInvalidateRelcacheByRelid(relid);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
Fix violations of CatalogTupleInsert/Update/Delete abstraction. In commits 2f5c9d9c9 and ab0289651 we invented an abstraction layer to insulate catalog manipulations from direct heap update calls. But evidently some patches that hadn't landed in-tree at that point didn't get the memo completely. Fix a couple of direct calls to simple_heap_delete to use CatalogTupleDelete instead; these appear to have been added in commits 7c4f52409 and 7b504eb28. This change is purely cosmetic ATM, but there's no point in having an abstraction layer if we allow random code to break it. Masahiko Sawada and Tom Lane Discussion: https://postgr.es/m/CAD21AoDOPRSVcwbnCN3Y1n_68ATyTspsU6=ygtHz_uY0VcdZ8A@mail.gmail.com
2017-06-14 16:26:46 +02:00
CatalogTupleDelete(relation, &tup->t_self);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
ReleaseSysCache(tup);
Lock table in DROP STATISTICS The DROP STATISTICS code failed to properly lock the table, leading to ERROR: tuple concurrently deleted when executed concurrently with ANALYZE. Fixed by modifying RemoveStatisticsById() to acquire the same lock as ANALYZE. This function is called only by DROP STATISTICS, as ANALYZE calls RemoveStatisticsDataById() directly. Reported by Justin Pryzby, fix by me. Backpatch through 12. The code was like this since it was introduced in 10, but older releases are EOL. Reported-by: Justin Pryzby Reviewed-by: Tom Lane Backpatch-through: 12 Discussion: https://postgr.es/m/ZUuk-8CfbYeq6g_u@pryzbyj2023
2023-11-19 21:03:29 +01:00
/* Keep lock until the end of the transaction. */
table_close(rel, NoLock);
Replace uses of heap_open et al with the corresponding table_* function. Author: Andres Freund Discussion: https://postgr.es/m/20190111000539.xbv7s6w7ilcvm7dp@alap3.anarazel.de
2019-01-21 19:32:19 +01:00
table_close(relation, RowExclusiveLock);
Implement multivariate n-distinct coefficients Add support for explicitly declared statistic objects (CREATE STATISTICS), allowing collection of statistics on more complex combinations that individual table columns. Companion commands DROP STATISTICS and ALTER STATISTICS ... OWNER TO / SET SCHEMA / RENAME are added too. All this DDL has been designed so that more statistic types can be added later on, such as multivariate most-common-values and multivariate histograms between columns of a single table, leaving room for permitting columns on multiple tables, too, as well as expressions. This commit only adds support for collection of n-distinct coefficient on user-specified sets of columns in a single table. This is useful to estimate number of distinct groups in GROUP BY and DISTINCT clauses; estimation errors there can cause over-allocation of memory in hashed aggregates, for instance, so it's a worthwhile problem to solve. A new special pseudo-type pg_ndistinct is used. (num-distinct estimation was deemed sufficiently useful by itself that this is worthwhile even if no further statistic types are added immediately; so much so that another version of essentially the same functionality was submitted by Kyotaro Horiguchi: https://postgr.es/m/20150828.173334.114731693.horiguchi.kyotaro@lab.ntt.co.jp though this commit does not use that code.) Author: Tomas Vondra. Some code rework by Álvaro. Reviewed-by: Dean Rasheed, David Rowley, Kyotaro Horiguchi, Jeff Janes, Ideriha Takeshi Discussion: https://postgr.es/m/543AFA15.4080608@fuzzy.cz https://postgr.es/m/20170320190220.ixlaueanxegqd5gr@alvherre.pgsql
2017-03-24 18:06:10 +01:00
}
Fix handling of extended statistics during ALTER COLUMN TYPE. ALTER COLUMN TYPE on a column used by a statistics object fails since commit 928c4de30, because the relevant switch in ATExecAlterColumnType is unprepared for columns to have dependencies from OCLASS_STATISTIC_EXT objects. Although the existing types of extended statistics don't actually need us to do any work for a column type change, it seems completely indefensible that that assumption is hidden behind the failure of an unrelated module to contain any code for the case. Hence, create and call an API function in statscmds.c where the assumption can be explained, and where we could add code to deal with the problem when it inevitably becomes real. Also, the reason this wasn't handled before, neither for extended stats nor for the last half-dozen new OCLASS kinds :-(, is that the default: in that switch suppresses compiler warnings, allowing people to miss the need to consider it when adding an OCLASS. We don't really need a default because surely getObjectClass should only return valid values of the enum; so remove it, and add the missed OCLASS entries where they should be. Discussion: https://postgr.es/m/20170512221010.nglatgt5azzdxjlj@alvherre.pgsql
2017-05-14 18:22:16 +02:00
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
/*
Clarify use of "statistics objects" in the code The code inconsistently used "statistic object" or "statistics" where the correct term, as discussed, is actually "statistics object". This improves the state of the code to be more consistent. While on it, fix an incorrect error message introduced in a4d75c8. This error should never happen, as the code states, but it would be misleading. Author: Justin Pryzby Reviewed-by: Álvaro Herrera, Michael Paquier Discussion: https://postgr.es/m/20210924215827.GS831@telsasoft.com Backpatch-through: 14
2021-09-29 08:29:38 +02:00
* Select a nonconflicting name for a new statistics object.
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
*
* name1, name2, and label are used the same way as for makeObjectName(),
* except that the label can't be NULL; digits will be appended to the label
* if needed to create a name that is unique within the specified namespace.
*
* Returns a palloc'd string.
*
* Note: it is theoretically possible to get a collision anyway, if someone
* else chooses the same name concurrently. This is fairly unlikely to be
* a problem in practice, especially if one is holding a share update
* exclusive lock on the relation identified by name1. However, if choosing
* multiple names within a single command, you'd better create the new object
* and do CommandCounterIncrement before choosing the next one!
*/
static char *
ChooseExtendedStatisticName(const char *name1, const char *name2,
const char *label, Oid namespaceid)
{
int pass = 0;
char *stxname = NULL;
char modlabel[NAMEDATALEN];
/* try the unmodified label first */
Replace remaining StrNCpy() by strlcpy() They are equivalent, except that StrNCpy() zero-fills the entire destination buffer instead of providing just one trailing zero. For all but a tiny number of callers, that's just overhead rather than being desirable. Remove StrNCpy() as it is now unused. In some cases, namestrcpy() is the more appropriate function to use. While we're here, simplify the API of namestrcpy(): Remove the return value, don't check for NULL input. Nothing was using that anyway. Also, remove a few unused name-related functions. Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://www.postgresql.org/message-id/flat/44f5e198-36f6-6cdb-7fa9-60e34784daae%402ndquadrant.com
2020-08-10 18:51:31 +02:00
strlcpy(modlabel, label, sizeof(modlabel));
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
for (;;)
{
Oid existingstats;
stxname = makeObjectName(name1, name2, modlabel);
Remove WITH OIDS support, change oid catalog column visibility. Previously tables declared WITH OIDS, including a significant fraction of the catalog tables, stored the oid column not as a normal column, but as part of the tuple header. This special column was not shown by default, which was somewhat odd, as it's often (consider e.g. pg_class.oid) one of the more important parts of a row. Neither pg_dump nor COPY included the contents of the oid column by default. The fact that the oid column was not an ordinary column necessitated a significant amount of special case code to support oid columns. That already was painful for the existing, but upcoming work aiming to make table storage pluggable, would have required expanding and duplicating that "specialness" significantly. WITH OIDS has been deprecated since 2005 (commit ff02d0a05280e0). Remove it. Removing includes: - CREATE TABLE and ALTER TABLE syntax for declaring the table to be WITH OIDS has been removed (WITH (oids[ = true]) will error out) - pg_dump does not support dumping tables declared WITH OIDS and will issue a warning when dumping one (and ignore the oid column). - restoring an pg_dump archive with pg_restore will warn when restoring a table with oid contents (and ignore the oid column) - COPY will refuse to load binary dump that includes oids. - pg_upgrade will error out when encountering tables declared WITH OIDS, they have to be altered to remove the oid column first. - Functionality to access the oid of the last inserted row (like plpgsql's RESULT_OID, spi's SPI_lastoid, ...) has been removed. The syntax for declaring a table WITHOUT OIDS (or WITH (oids = false) for CREATE TABLE) is still supported. While that requires a bit of support code, it seems unnecessary to break applications / dumps that do not use oids, and are explicit about not using them. The biggest user of WITH OID columns was postgres' catalog. This commit changes all 'magic' oid columns to be columns that are normally declared and stored. To reduce unnecessary query breakage all the newly added columns are still named 'oid', even if a table's column naming scheme would indicate 'reloid' or such. This obviously requires adapting a lot code, mostly replacing oid access via HeapTupleGetOid() with access to the underlying Form_pg_*->oid column. The bootstrap process now assigns oids for all oid columns in genbki.pl that do not have an explicit value (starting at the largest oid previously used), only oids assigned later by oids will be above FirstBootstrapObjectId. As the oid column now is a normal column the special bootstrap syntax for oids has been removed. Oids are not automatically assigned during insertion anymore, all backend code explicitly assigns oids with GetNewOidWithIndex(). For the rare case that insertions into the catalog via SQL are called for the new pg_nextoid() function can be used (which only works on catalog tables). The fact that oid columns on system tables are now normal columns means that they will be included in the set of columns expanded by * (i.e. SELECT * FROM pg_class will now include the table's oid, previously it did not). It'd not technically be hard to hide oid column by default, but that'd mean confusing behavior would either have to be carried forward forever, or it'd cause breakage down the line. While it's not unlikely that further adjustments are needed, the scope/invasiveness of the patch makes it worthwhile to get merge this now. It's painful to maintain externally, too complicated to commit after the code code freeze, and a dependency of a number of other patches. Catversion bump, for obvious reasons. Author: Andres Freund, with contributions by John Naylor Discussion: https://postgr.es/m/20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de
2018-11-21 00:36:57 +01:00
existingstats = GetSysCacheOid2(STATEXTNAMENSP, Anum_pg_statistic_ext_oid,
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
PointerGetDatum(stxname),
ObjectIdGetDatum(namespaceid));
if (!OidIsValid(existingstats))
break;
/* found a conflict, so try a new name component */
pfree(stxname);
snprintf(modlabel, sizeof(modlabel), "%s%d", label, ++pass);
}
return stxname;
}
/*
Clarify use of "statistics objects" in the code The code inconsistently used "statistic object" or "statistics" where the correct term, as discussed, is actually "statistics object". This improves the state of the code to be more consistent. While on it, fix an incorrect error message introduced in a4d75c8. This error should never happen, as the code states, but it would be misleading. Author: Justin Pryzby Reviewed-by: Álvaro Herrera, Michael Paquier Discussion: https://postgr.es/m/20210924215827.GS831@telsasoft.com Backpatch-through: 14
2021-09-29 08:29:38 +02:00
* Generate "name2" for a new statistics object given the list of column
* names for it. This will be passed to ChooseExtendedStatisticName along
* with the parent table name and a suitable label.
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
*
* We know that less than NAMEDATALEN characters will actually be used,
* so we can truncate the result once we've generated that many.
*
Include all columns in default names for foreign key constraints When creating a name for a foreign key constraint when none is specified, use all column names instead of only the first one, similar to how it is already done for index names. Author: Paul Martinez <hellopfm@gmail.com> Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com> Discussion: https://www.postgresql.org/message-id/flat/CAF+2_SFjky6XRfLNRXpkG97W6PRbOO_mjAxqXzAAimU=c7w7_A@mail.gmail.com
2019-03-13 14:15:37 +01:00
* XXX see also ChooseForeignKeyConstraintNameAddition and
* ChooseIndexNameAddition.
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
*/
static char *
ChooseExtendedStatisticNameAddition(List *exprs)
{
char buf[NAMEDATALEN * 2];
int buflen = 0;
ListCell *lc;
buf[0] = '\0';
foreach(lc, exprs)
{
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
StatsElem *selem = (StatsElem *) lfirst(lc);
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
const char *name;
/* It should be one of these, but just skip if it happens not to be */
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
if (!IsA(selem, StatsElem))
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
continue;
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
name = selem->name;
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
if (buflen > 0)
buf[buflen++] = '_'; /* insert _ between names */
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/*
* We use fixed 'expr' for expressions, which have empty column names.
* For indexes this is handled in ChooseIndexColumnNames, but we have
* no such function for stats and it does not seem worth adding. If a
* better name is needed, the user can specify it explicitly.
*/
if (!name)
name = "expr";
Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL) The LIKE INCLUDING ALL clause to CREATE TABLE intuitively indicates cloning of extended statistics on the source table, but it failed to do so. Patch it up so that it does. Also include an INCLUDING STATISTICS option to the LIKE clause, so that the behavior can be requested individually, or excluded individually. While at it, reorder the INCLUDING options, both in code and in docs, in alphabetical order which makes more sense than feature-implementation order that was previously used. Backpatch this to Postgres 10, where extended statistics were introduced, because this is seen as an oversight in a fresh feature which is better to get consistent from the get-go instead of changing only in pg11. In pg11, comments on statistics objects are cloned too. In pg10 they are not, because I (Álvaro) was too coward to change the parse node as required to support it. Also, in pg10 I chose not to renumber the parser symbols for the various INCLUDING options in LIKE, for the same reason. Any corresponding user-visible changes (docs) are backpatched, though. Reported-by: Stephen Froehlich Author: David Rowley Reviewed-by: Álvaro Herrera, Tomas Vondra Discussion: https://postgr.es/m/CY1PR0601MB1927315B45667A1B679D0FD5E5EF0@CY1PR0601MB1927.namprd06.prod.outlook.com
2018-03-05 23:37:19 +01:00
/*
* At this point we have buflen <= NAMEDATALEN. name should be less
* than NAMEDATALEN already, but use strlcpy for paranoia.
*/
strlcpy(buf + buflen, name, NAMEDATALEN);
buflen += strlen(buf + buflen);
if (buflen >= NAMEDATALEN)
break;
}
return pstrdup(buf);
}
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
/*
Clarify use of "statistics objects" in the code The code inconsistently used "statistic object" or "statistics" where the correct term, as discussed, is actually "statistics object". This improves the state of the code to be more consistent. While on it, fix an incorrect error message introduced in a4d75c8. This error should never happen, as the code states, but it would be misleading. Author: Justin Pryzby Reviewed-by: Álvaro Herrera, Michael Paquier Discussion: https://postgr.es/m/20210924215827.GS831@telsasoft.com Backpatch-through: 14
2021-09-29 08:29:38 +02:00
* StatisticsGetRelation: given a statistics object's OID, get the OID of
* the relation it is defined on. Uses the system cache.
Extended statistics on expressions Allow defining extended statistics on expressions, not just just on simple column references. With this commit, expressions are supported by all existing extended statistics kinds, improving the same types of estimates. A simple example may look like this: CREATE TABLE t (a int); CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t; ANALYZE t; The collected statistics are useful e.g. to estimate queries with those expressions in WHERE or GROUP BY clauses: SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0; SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20); This introduces new internal statistics kind 'e' (expressions) which is built automatically when the statistics object definition includes any expressions. This represents single-expression statistics, as if there was an expression index (but without the index maintenance overhead). The statistics is stored in pg_statistics_ext_data as an array of composite types, which is possible thanks to 79f6a942bd. CREATE STATISTICS allows building statistics on a single expression, in which case in which case it's not possible to specify statistics kinds. A new system view pg_stats_ext_exprs can be used to display expression statistics, similarly to pg_stats and pg_stats_ext views. ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it treats indexes, i.e. it drops and recreates the statistics. This means all statistics are reset, and we no longer try to preserve at least the functional dependencies. This should not be a major issue in practice, as the functional dependencies actually rely on per-column statistics, which were always reset anyway. Author: Tomas Vondra Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com
2021-03-26 23:22:01 +01:00
*/
Oid
StatisticsGetRelation(Oid statId, bool missing_ok)
{
HeapTuple tuple;
Form_pg_statistic_ext stx;
Oid result;
tuple = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(statId));
if (!HeapTupleIsValid(tuple))
{
if (missing_ok)
return InvalidOid;
elog(ERROR, "cache lookup failed for statistics object %u", statId);
}
stx = (Form_pg_statistic_ext) GETSTRUCT(tuple);
Assert(stx->oid == statId);
result = stx->stxrelid;
ReleaseSysCache(tuple);
return result;
}