Commit Graph

294 Commits

Author SHA1 Message Date
Alvaro Herrera 790bf615dd
Remove ALL keyword from TABLES IN SCHEMA for publication
This may be a bit too subtle, but removing that word from there makes
this clause no longer a perfect parallel of the GRANT variant "ALL
TABLES IN SCHEMA": indeed, for publications what we record is the schema
itself, not the tables therein, which means that any tables added to the
schema in the future are also published.  This is completely different
to what GRANT does, which is affect only the tables that exist when the
command is executed.

There isn't resounding support for this change, but there are a few
positive votes and no opposition.  Because the time to 15 RC1 is very
short, let's get this out now.

Backpatch to 15.

Discussion: https://postgr.es/m/2729c9e2-9aac-8cda-f2f4-34f2bcc18f4e
2022-09-22 19:02:25 +02:00
Tom Lane 70988b7b0a Improve makeArrayTypeName's algorithm for choosing array type names.
As before, we start by prepending one underscore (truncating the
base name if necessary).  But if there is a conflict, then instead of
prepending more and more underscores, append an underscore and some
digits, in much the same way that ChooseRelationName does.  While
the previous logic could be driven to fail by creating a lot of
types with long names differing only near the end, this version seems
certain enough to eventually succeed that we can remove the failure
code path that was there before.

While at it, undo 6df7a9698's decision to split this code out of
makeArrayTypeName.  That wasn't actually accomplishing anything,
because no other function was using it --- and it would have been
wrong to do so.  The convention that a prefix "_" means an array,
not something else, is too ancient to mess with.

Andrey Lepikhov and Dmitry Koval, reviewed by Masahiko Sawada and myself

Discussion: https://postgr.es/m/b84cd82c-cc67-198a-8b1c-60f44e1259ad@postgrespro.ru
2022-07-26 15:38:09 -04:00
Peter Eisentraut 784cedda06 Allow specifying STORAGE attribute for a new table
Previously, the STORAGE specification was only available in ALTER
TABLE.  This makes it available in CREATE TABLE as well.

Also make the code and the documentation for STORAGE and COMPRESSION
attributes consistent.

Author:	Teodor Sigaev <teodor@sigaev.ru>
Author: Aleksander Alekseev <aleksander@timescale.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: wenjing zeng <wjzeng2012@gmail.com>
Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/de83407a-ae3d-a8e1-a788-920eb334f25b@sigaev.ru
2022-07-13 12:21:45 +02:00
Peter Eisentraut 344d62fb9a Unlogged sequences
Add support for unlogged sequences.  Unlike for unlogged tables, this
is not a performance feature.  It allows sequences associated with
unlogged tables to be excluded from replication.

A new subcommand ALTER SEQUENCE ... SET LOGGED/UNLOGGED is added.

An identity/serial sequence now automatically gets and follows the
persistence level (logged/unlogged) of its owning table.  (The
sequences owned by temporary tables were already temporary through the
separate mechanism in RangeVarAdjustRelationPersistence().)  But you
can still change the persistence of an owned sequence separately.
Also, pg_dump and pg_upgrade preserve the persistence of existing
sequences.

Discussion: https://www.postgresql.org/message-id/flat/04e12818-2f98-257c-b926-2845d74ed04f%402ndquadrant.com
2022-04-07 16:18:00 +02:00
Peter Eisentraut ae63017bdb Preparatory test cleanup
Add a little bit of explanation, clarity, and space.  Extraced from a
larger patch so that the changes from that patch would be easier to
identify.

Discussion: https://www.postgresql.org/message-id/flat/04e12818-2f98-257c-b926-2845d74ed04f%402ndquadrant.com
2022-03-28 15:22:34 +02:00
Tom Lane 641f3dffcd Restore the previous semantics of get_constraint_index().
Commit 8b069ef5d changed this function to look at pg_constraint.conindid
rather than searching pg_depend.  That was a good performance improvement,
but it failed to preserve the exact semantics.  The old code would only
return an index that was "owned by" (internally dependent on) the
specified constraint, whereas the new code will also return indexes that
are just referenced by foreign key constraints.  This confuses ALTER
TABLE, which was implicitly expecting the previous semantics, into
failing with errors like
    ERROR:  relation 146621 has multiple clustered indexes
or
    ERROR:  "pk_attbl" is not an index for table "atref"

We can fix this without reverting the performance improvement by adding
a contype check in get_constraint_index().  Another way could be to
make ALTER TABLE check it, but I'm worried that extension code could
also have subtle dependencies on the old semantics.

Tom Lane and Japin Li, per bug #17409 from Holly Roberts.
Back-patch to v14 where the error crept in.

Discussion: https://postgr.es/m/17409-52871dda8b5741cb@postgresql.org
2022-03-11 13:47:29 -05:00
Tom Lane 7ead9925ff Prevent altering partitioned table's rowtype, if it's used elsewhere.
We disallow altering a column datatype within a regular table,
if the table's rowtype is used as a column type elsewhere,
because we lack code to go around and rewrite the other tables.
This restriction should apply to partitioned tables as well, but it
was not checked because ATRewriteTables and ATPrepAlterColumnType
were not on the same page about who should do it for which relkinds.

Per bug #17351 from Alexander Lakhin.  Back-patch to all supported
branches.

Discussion: https://postgr.es/m/17351-6db1870f3f4f612a@postgresql.org
2022-01-06 16:46:46 -05:00
Amit Kapila 5a2832465f Allow publishing the tables of schema.
A new option "FOR ALL TABLES IN SCHEMA" in Create/Alter Publication allows
one or more schemas to be specified, whose tables are selected by the
publisher for sending the data to the subscriber.

The new syntax allows specifying both the tables and schemas. For example:
CREATE PUBLICATION pub1 FOR TABLE t1,t2,t3, ALL TABLES IN SCHEMA s1,s2;
OR
ALTER PUBLICATION pub1 ADD TABLE t1,t2,t3, ALL TABLES IN SCHEMA s1,s2;

A new system table "pg_publication_namespace" has been added, to maintain
the schemas that the user wants to publish through the publication.
Modified the output plugin (pgoutput) to publish the changes if the
relation is part of schema publication.

Updates pg_dump to identify and dump schema publications. Updates the \d
family of commands to display schema publications and \dRp+ variant will
now display associated schemas if any.

Author: Vignesh C, Hou Zhijie, Amit Kapila
Syntax-Suggested-by: Tom Lane, Alvaro Herrera
Reviewed-by: Greg Nancarrow, Masahiko Sawada, Hou Zhijie, Amit Kapila, Haiying Tang, Ajin Cherian, Rahila Syed, Bharath Rupireddy, Mark Dilger
Tested-by: Haiying Tang
Discussion: https://www.postgresql.org/message-id/CALDaNm0OANxuJ6RXqwZsM1MSY4s19nuH3734j4a72etDwvBETQ@mail.gmail.com
2021-10-27 07:44:52 +05:30
Alvaro Herrera cd124d205c
Protect against collation variations in test
Discussion: https://postgr.es/m/YW/MYdSRQZtPFBWR@paquier.xyz
2021-10-20 13:05:42 -03:00
Alvaro Herrera c2c618ff11
Ensure correct lock level is used in ALTER ... RENAME
Commit 1b5d797cd4 intended to relax the lock level used to rename
indexes, but inadvertently allowed *any* relation to be renamed with a
lowered lock level, as long as the command is spelled ALTER INDEX.
That's undesirable for other relation types, so retry the operation with
the higher lock if the relation turns out not to be an index.

After this fix, ALTER INDEX <sometable> RENAME will require access
exclusive lock, which it didn't before.

Author: Nathan Bossart <bossartn@amazon.com>
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reported-by: Onder Kalaci <onderk@microsoft.com>
Discussion: https://postgr.es/m/PH0PR21MB1328189E2821CDEC646F8178D8AE9@PH0PR21MB1328.namprd21.prod.outlook.com
2021-10-19 19:08:45 -03:00
Alvaro Herrera d6f1e16c8f
Invalidate partitions of table being attached/detached
Failing to do that, any direct inserts/updates of those partitions
would fail to enforce the correct constraint, that is, one that
considers the new partition constraint of their parent table.

Backpatch to 10.

Reported by: Hou Zhijie <houzj.fnst@fujitsu.com>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Nitin Jadhav <nitinjadhavpostgres@gmail.com>
Reviewed-by: Pavel Borisov <pashkin.elfe@gmail.com>

Discussion: https://postgr.es/m/OS3PR01MB5718DA1C4609A25186D1FBF194089%40OS3PR01MB5718.jpnprd01.prod.outlook.com
2021-10-18 19:08:25 -03:00
Fujii Masao 170aec63cd Avoid using ambiguous word "positive" in error message.
There are two identical error messages about valid value of modulus for
hash partition, in PostgreSQL source code. Commit 0e1275fb07 improved
only one of them so that ambiguous word "positive" was avoided there,
and forgot to improve the other. This commit improves the other.
Which would reduce translator burden.

Back-pach to v11 where the error message exists.

Author: Kyotaro Horiguchi
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/20210819.170315.1413060634876301811.horikyota.ntt@gmail.com
2021-08-25 11:46:25 +09:00
Peter Eisentraut 2ed532ee8c 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 09:44:51 +02:00
Alvaro Herrera 7b357cc6ae
Don't add a redundant constraint when detaching a partition
On ALTER TABLE .. DETACH CONCURRENTLY, we add a new table constraint
that duplicates the partition constraint.  But if the partition already
has another constraint that implies that one, then that's unnecessary.
We were already avoiding the addition of a duplicate constraint if there
was an exact 'equal' match -- this just improves the quality of the check.

Author: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20210410184226.GY6592@telsasoft.com
2021-04-21 18:12:05 -04:00
Alvaro Herrera 71f4c8c6f7
ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY
Allow a partition be detached from its partitioned table without
blocking concurrent queries, by running in two transactions and only
requiring ShareUpdateExclusive in the partitioned table.

Because it runs in two transactions, it cannot be used in a transaction
block.  This is the main reason to use dedicated syntax: so that users
can choose to use the original mode if they need it.  But also, it
doesn't work when a default partition exists (because an exclusive lock
would still need to be obtained on it, in order to change its partition
constraint.)

In case the second transaction is cancelled or a crash occurs, there's
ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final
steps.

The main trick to make this work is the addition of column
pg_inherits.inhdetachpending, initially false; can only be set true in
the first part of this command.  Once that is committed, concurrent
transactions that use a PartitionDirectory will include or ignore
partitions so marked: in optimizer they are ignored if the row is marked
committed for the snapshot; in executor they are always included.  As a
result, and because of the way PartitionDirectory caches partition
descriptors, queries that were planned before the detach will see the
rows in the detached partition and queries that are planned after the
detach, won't.

A CHECK constraint is created that duplicates the partition constraint.
This is probably not strictly necessary, and some users will prefer to
remove it afterwards, but if the partition is re-attached to a
partitioned table, the constraint needn't be rechecked.

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql
2021-03-25 18:00:28 -03:00
Peter Eisentraut efbfb64241 Improve new hash partition bound check error messages
For the error message "every hash partition modulus must be a factor
of the next larger modulus", add a detail message that shows the
particular numbers and existing partition involved.  Also comment the
code more.

Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Discussion: https://www.postgresql.org/message-id/flat/bb9d60b4-aadb-607a-1a9d-fdc3434dddcd%40enterprisedb.com
2021-02-22 08:06:45 +01:00
Tom Lane 6b2c4e59d0 Improve error cursor positions for problems with partition bounds.
We failed to pass down the query string to check_new_partition_bound,
so that its attempts to provide error cursor positions were for naught;
one must have the query string to get parser_errposition to do anything.
Adjust its API to require a ParseState to be passed down.

Also, improve the logic inside check_new_partition_bound so that the
cursor points at the partition bound for the specific column causing
the issue, when one can be identified.

That part is also for naught if we can't determine the query position of
the column with the problem.  Improve transformPartitionBoundValue so
that it makes sure that const-simplified partition expressions will be
properly labeled with positions.  In passing, skip calling evaluate_expr
if the value is already a Const, which is surely the most common case.

Alexandra Wang, Ashwin Agrawal, Amit Langote; reviewed by Ashutosh Bapat

Discussion: https://postgr.es/m/CACiyaSopZoqssfMzgHk6fAkp01cL6vnqBdmTw2C5_KJaFR_aMg@mail.gmail.com
Discussion: https://postgr.es/m/CAJV4CdrZ5mKuaEsRSbLf2URQ3h6iMtKD=hik8MaF5WwdmC9uZw@mail.gmail.com
2020-09-23 18:04:53 -04:00
Tom Lane 5b02d68e75 Fix ALTER TABLE's scheduling rules for AT_AddConstraint subcommands.
Commit 1281a5c90 rearranged the logic in this area rather drastically,
and it broke the case of adding a foreign key constraint in the same
ALTER that adds the pkey or unique constraint it depends on.  While
self-referential fkeys are surely a pretty niche case, this used to
work so we shouldn't break it.

To fix, reorganize the scheduling rules in ATParseTransformCmd so
that a transformed AT_AddConstraint subcommand will be delayed into
a later pass in all cases, not only when it's been spit out as a
side-effect of parsing some other command type.

Also tweak the logic so that we won't run ATParseTransformCmd twice
while doing this.  It seems to work even without that, but it's
surely wasting cycles to do so.

Per bug #16589 from Jeremy Evans.  Back-patch to v13 where the new
code was introduced.

Discussion: https://postgr.es/m/16589-31c8d981ca503896@postgresql.org
2020-08-22 12:34:17 -04:00
David Rowley f1fcf2d3b2 Fix timing issue with ALTER TABLE's validate constraint
An ALTER TABLE to validate a foreign key in which another subcommand
already caused a pending table rewrite could fail due to ALTER TABLE
attempting to validate the foreign key before the actual table rewrite
takes place.  This situation could result in an error such as:

ERROR:  could not read block 0 in file "base/nnnnn/nnnnn": read only 0 of 8192 bytes

The failure here was due to the SPI call which validates the foreign key
trying to access an index which is yet to be rebuilt.

Similarly, we also incorrectly tried to validate CHECK constraints before
the heap had been rewritten.

The fix for both is to delay constraint validation until phase 3, after
the table has been rewritten.  For CHECK constraints this means a slight
behavioral change.  Previously ALTER TABLE VALIDATE CONSTRAINT on
inheritance tables would be validated from the bottom up.  This was
different from the order of evaluation when a new CHECK constraint was
added.  The changes made here aligns the VALIDATE CONSTRAINT evaluation
order for inheritance tables to be the same as ADD CONSTRAINT, which is
generally top-down.

Reported-by: Nazli Ugur Koyluoglu, using SQLancer
Discussion: https://postgr.es/m/CAApHDvp%3DZXv8wiRyk_0rWr00skhGkt8vXDrHJYXRMft3TjkxCA%40mail.gmail.com
Backpatch-through: 9.5 (all supported versions)
2020-07-14 16:55:35 +12:00
Heikki Linnakangas 0099db4ce1 Fix typo in test comment.
The same comment was copied to a few different places, with the same typo.
Backpatch down to v11, where this typo was introduced.
2020-05-28 12:35:18 +03:00
Peter Eisentraut 501e41dd3c Propagate ALTER TABLE ... SET STORAGE to indexes
When creating a new index, the attstorage setting of the table column
is copied to regular (non-expression) index columns.  But a later
ALTER TABLE ... SET STORAGE is not propagated to indexes, thus
creating an inconsistent and undumpable state.

Discussion: https://www.postgresql.org/message-id/flat/9765d72b-37c0-06f5-e349-2a580aafd989%402ndquadrant.com
2020-05-08 08:39:17 +02:00
Thomas Munro 4c04be9b05 Introduce xid8-based functions to replace txid_XXX.
The txid_XXX family of fmgr functions exposes 64 bit transaction IDs to
users as int8.  Now that we have an SQL type xid8 for FullTransactionId,
define a new set of functions including pg_current_xact_id() and
pg_current_snapshot() based on that.  Keep the old functions around too,
for now.

It's a bit sneaky to use the same C functions for both, but since the
binary representation is identical except for the signedness of the
type, and since older functions are the ones using the wrong signedness,
and since we'll presumably drop the older ones after a reasonable period
of time, it seems reasonable to switch to FullTransactionId internally
and share the code for both.

Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: Takao Fujii <btfujiitkp@oss.nttdata.com>
Reviewed-by: Yoshikazu Imai <imai.yoshikazu@fujitsu.com>
Reviewed-by: Mark Dilger <mark.dilger@enterprisedb.com>
Discussion: https://postgr.es/m/20190725000636.666m5mad25wfbrri%40alap3.anarazel.de
2020-04-07 12:04:32 +12:00
Michael Paquier a40caf5f86 Preserve clustered index after rewrites with ALTER TABLE
A table rewritten by ALTER TABLE would lose tracking of an index usable
for CLUSTER.  This setting is tracked by pg_index.indisclustered and is
controlled by ALTER TABLE, so some extra work was needed to restore it
properly.  Note that ALTER TABLE only marks the index that can be used
for clustering, and does not do the actual operation.

Author: Amit Langote, Justin Pryzby
Reviewed-by: Ibrar Ahmed, Michael Paquier
Discussion: https://postgr.es/m/20200202161718.GI13621@telsasoft.com
Backpatch-through: 9.5
2020-04-06 11:03:49 +09:00
Noah Misch c6b92041d3 Skip WAL for new relfilenodes, under wal_level=minimal.
Until now, only selected bulk operations (e.g. COPY) did this.  If a
given relfilenode received both a WAL-skipping COPY and a WAL-logged
operation (e.g. INSERT), recovery could lose tuples from the COPY.  See
src/backend/access/transam/README section "Skipping WAL for New
RelFileNode" for the new coding rules.  Maintainers of table access
methods should examine that section.

To maintain data durability, just before commit, we choose between an
fsync of the relfilenode and copying its contents to WAL.  A new GUC,
wal_skip_threshold, guides that choice.  If this change slows a workload
that creates small, permanent relfilenodes under wal_level=minimal, try
adjusting wal_skip_threshold.  Users setting a timeout on COMMIT may
need to adjust that timeout, and log_min_duration_statement analysis
will reflect time consumption moving to COMMIT from commands like COPY.

Internally, this requires a reliable determination of whether
RollbackAndReleaseCurrentSubTransaction() would unlink a relation's
current relfilenode.  Introduce rd_firstRelfilenodeSubid.  Amend the
specification of rd_createSubid such that the field is zero when a new
rel has an old rd_node.  Make relcache.c retain entries for certain
dropped relations until end of transaction.

Bump XLOG_PAGE_MAGIC, since this introduces XLOG_GIST_ASSIGN_LSN.
Future servers accept older WAL, so this bump is discretionary.

Kyotaro Horiguchi, reviewed (in earlier, similar versions) by Robert
Haas.  Heikki Linnakangas and Michael Paquier implemented earlier
designs that materially clarified the problem.  Reviewed, in earlier
designs, by Andrew Dunstan, Andres Freund, Alvaro Herrera, Tom Lane,
Fujii Masao, and Simon Riggs.  Reported by Martijn van Oosterhout.

Discussion: https://postgr.es/m/20150702220524.GA9392@svana.org
2020-04-04 12:25:34 -07:00
Noah Misch de9396326e Revert "Skip WAL for new relfilenodes, under wal_level=minimal."
This reverts commit cb2fd7eac2.  Per
numerous buildfarm members, it was incompatible with parallel query, and
a test case assumed LP64.  Back-patch to 9.5 (all supported versions).

Discussion: https://postgr.es/m/20200321224920.GB1763544@rfd.leadboat.com
2020-03-22 09:24:09 -07:00
Noah Misch cb2fd7eac2 Skip WAL for new relfilenodes, under wal_level=minimal.
Until now, only selected bulk operations (e.g. COPY) did this.  If a
given relfilenode received both a WAL-skipping COPY and a WAL-logged
operation (e.g. INSERT), recovery could lose tuples from the COPY.  See
src/backend/access/transam/README section "Skipping WAL for New
RelFileNode" for the new coding rules.  Maintainers of table access
methods should examine that section.

To maintain data durability, just before commit, we choose between an
fsync of the relfilenode and copying its contents to WAL.  A new GUC,
wal_skip_threshold, guides that choice.  If this change slows a workload
that creates small, permanent relfilenodes under wal_level=minimal, try
adjusting wal_skip_threshold.  Users setting a timeout on COMMIT may
need to adjust that timeout, and log_min_duration_statement analysis
will reflect time consumption moving to COMMIT from commands like COPY.

Internally, this requires a reliable determination of whether
RollbackAndReleaseCurrentSubTransaction() would unlink a relation's
current relfilenode.  Introduce rd_firstRelfilenodeSubid.  Amend the
specification of rd_createSubid such that the field is zero when a new
rel has an old rd_node.  Make relcache.c retain entries for certain
dropped relations until end of transaction.

Back-patch to 9.5 (all supported versions).  This introduces a new WAL
record type, XLOG_GIST_ASSIGN_LSN, without bumping XLOG_PAGE_MAGIC.  As
always, update standby systems before master systems.  This changes
sizeof(RelationData) and sizeof(IndexStmt), breaking binary
compatibility for affected extensions.  (The most recent commit to
affect the same class of extensions was
089e4d405d0f3b94c74a2c6a54357a84a681754b.)

Kyotaro Horiguchi, reviewed (in earlier, similar versions) by Robert
Haas.  Heikki Linnakangas and Michael Paquier implemented earlier
designs that materially clarified the problem.  Reviewed, in earlier
designs, by Andrew Dunstan, Andres Freund, Alvaro Herrera, Tom Lane,
Fujii Masao, and Simon Riggs.  Reported by Martijn van Oosterhout.

Discussion: https://postgr.es/m/20150702220524.GA9392@svana.org
2020-03-21 09:38:26 -07:00
Andrew Gierth bf6cc19e34 Force tuple conversion when the source has missing attributes.
Tuple conversion incorrectly concluded that no conversion was needed
as long as all the attributes lined up. But if the source tuple has a
missing attribute (from addition of a column with default), then the
destination tupdesc might not reflect the same default. The typical
symptom was that the affected columns would be unexpectedly NULL.

Repair by always forcing conversion if the source has missing
attributes, which will be filled in by the deform operation. (In
theory we could optimize for when the destination has the same
default, but that seemed overkill.)

Backpatch to 11 where missing attributes were added.

Per bug #16242.

Vik Fearing (discovery, code, testing) and me (analysis, testcase).

Discussion: https://postgr.es/m/16242-d1c9fca28445966b@postgresql.org
2020-02-05 20:21:20 +00:00
Amit Kapila 05f18c6b6b Added relation name in error messages for constraint checks.
This gives more information to the user about the error and it makes such
messages consistent with the other similar messages in the code.

Reported-by: Simon Riggs
Author: Mahendra Singh and Simon Riggs
Reviewed-by: Beena Emerson and Amit Kapila
Discussion: https://postgr.es/m/CANP8+j+7YUvQvGxTrCiw77R23enMJ7DFmyA3buR+fa2pKs4XhA@mail.gmail.com
2020-01-28 07:48:10 +05:30
Tom Lane 1281a5c907 Restructure ALTER TABLE execution to fix assorted bugs.
We've had numerous bug reports about how (1) IF NOT EXISTS clauses in
ALTER TABLE don't behave as-expected, and (2) combining certain actions
into one ALTER TABLE doesn't work, though executing the same actions as
separate statements does.  This patch cleans up all of the cases so far
reported from the field, though there are still some oddities associated
with identity columns.

The core problem behind all of these bugs is that we do parse analysis
of ALTER TABLE subcommands too soon, before starting execution of the
statement.  The root of the bugs in group (1) is that parse analysis
schedules derived commands (such as a CREATE SEQUENCE for a serial
column) before it's known whether the IF NOT EXISTS clause should cause
a subcommand to be skipped.  The root of the bugs in group (2) is that
earlier subcommands may change the catalog state that later subcommands
need to be parsed against.

Hence, postpone parse analysis of ALTER TABLE's subcommands, and do
that one subcommand at a time, during "phase 2" of ALTER TABLE which
is the phase that does catalog rewrites.  Thus the catalog effects
of earlier subcommands are already visible when we analyze later ones.
(The sole exception is that we do parse analysis for ALTER COLUMN TYPE
subcommands during phase 1, so that their USING expressions can be
parsed against the table's original state, which is what we need.
Arguably, these bugs stem from falsely concluding that because ALTER
COLUMN TYPE must do early parse analysis, every other command subtype
can too.)

This means that ALTER TABLE itself must deal with execution of any
non-ALTER-TABLE derived statements that are generated by parse analysis.
Add a suitable entry point to utility.c to accept those recursive
calls, and create a struct to pass through the information needed by
the recursive call, rather than making the argument lists of
AlterTable() and friends even longer.

Getting this to work correctly required a little bit of fiddling
with the subcommand pass structure, in particular breaking up
AT_PASS_ADD_CONSTR into multiple passes.  But otherwise it's mostly
a pretty straightforward application of the above ideas.

Fixing the residual issues for identity columns requires refactoring of
where the dependency link from an identity column to its sequence gets
set up.  So that seems like suitable material for a separate patch,
especially since this one is pretty big already.

Discussion: https://postgr.es/m/10365.1558909428@sss.pgh.pa.us
2020-01-15 18:49:24 -05:00
Tom Lane 6ef77cf46e Further adjust EXPLAIN's choices of table alias names.
This patch causes EXPLAIN to always assign a separate table alias to the
parent RTE of an append relation (inheritance set); before, such RTEs
were ignored if not actually scanned by the plan.  Since the child RTEs
now always have that same alias to start with (cf. commit 55a1954da),
the net effect is that the parent RTE usually gets the alias used or
implied by the query text, and the children all get that alias with "_N"
appended.  (The exception to "usually" is if there are duplicate aliases
in different subtrees of the original query; then some of those original
RTEs will also have "_N" appended.)

This results in more uniform output for partitioned-table plans than
we had before: the partitioned table itself gets the original alias,
and all child tables have aliases with "_N", rather than the previous
behavior where one of the children would get an alias without "_N".

The reason for giving the parent RTE an alias, even if it isn't scanned
by the plan, is that we now use the parent's alias to qualify Vars that
refer to an appendrel output column and appear above the Append or
MergeAppend that computes the appendrel.  But below the append, Vars
refer to some one of the child relations, and are displayed that way.
This seems clearer than the old behavior where a Var that could carry
values from any child relation was displayed as if it referred to only
one of them.

While at it, change ruleutils.c so that the code paths used by EXPLAIN
deal in Plan trees not PlanState trees.  This effectively reverts a
decision made in commit 1cc29fe7c, which seemed like a good idea at
the time to make ruleutils.c consistent with explain.c.  However,
it's problematic because we'd really like to allow executor startup
pruning to remove all the children of an append node when possible,
leaving no child PlanState to resolve Vars against.  (That's not done
here, but will be in the next patch.)  This requires different handling
of subplans and initplans than before, but is otherwise a pretty
straightforward change.

Discussion: https://postgr.es/m/001001d4f44b$2a2cca50$7e865ef0$@lab.ntt.co.jp
2019-12-11 17:05:18 -05:00
Tom Lane 55a1954da1 Fix EXPLAIN's column alias output for mismatched child tables.
If an inheritance/partitioning parent table is assigned some column
alias names in the query, EXPLAIN mapped those aliases onto the
child tables' columns by physical position, resulting in bogus output
if a child table's columns aren't one-for-one with the parent's.

To fix, make expand_single_inheritance_child() generate a correctly
re-mapped column alias list, rather than just copying the parent
RTE's alias node.  (We have to fill the alias field, not just
adjust the eref field, because ruleutils.c will ignore eref in
favor of looking at the real column names.)

This means that child tables will now always have alias fields in
plan rtables, where before they might not have.  That results in
a rather substantial set of regression test output changes:
EXPLAIN will now always show child tables with aliases that match
the parent table (usually with "_N" appended for uniqueness).
But that seems like a net positive for understandability, since
the parent alias corresponds to something that actually appeared
in the original query, while the child table names didn't.
(Note that this does not change anything for cases where an explicit
table alias was written in the query for the parent table; it
just makes cases without such aliases behave similarly to that.)
Hence, while we could avoid these subsidiary changes if we made
inherit.c more complicated, we choose not to.

Discussion: https://postgr.es/m/12424.1575168015@sss.pgh.pa.us
2019-12-02 19:08:10 -05:00
Peter Eisentraut 7fc380f83d Add a regression test for allow_system_table_mods
Add a regression test file that exercises the kinds of commands that
allow_system_table_mods allows.

This is put in the "unsafe_tests" suite, so it won't accidentally
create a mess if someone runs the normal regression tests against an
instance that they care about.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/8b00ea5e-28a7-88ba-e848-21528b632354%402ndquadrant.com
2019-11-29 10:22:13 +01:00
Andres Freund ae5cae54ca Replace alter_table.sql test usage of event triggers.
The test in 93765bd956 added an event trigger to ensure that the
tested table rewrites do not get optimized away (as happened in the
past). But doing so would require running the tests in isolation, as
otherwise the trigger might also fire in concurrent sessions, causing
test failures there.

Reported-By: Tom Lane
Discussion: https://postgr.es/m/3328.1570740683@sss.pgh.pa.us
Backpatch: 12, just as 93765bd956
2019-10-16 02:37:34 -07:00
Andres Freund 93765bd956 Fix table rewrites that include a column without a default.
In c2fe139c20 I made ATRewriteTable() use tuple slots. Unfortunately
I did not notice that columns can be added in a rewrite that do not
have a default, when another column is added/altered requiring one.

Initialize columns to NULL again, and add tests.

Bug: #16038
Reported-By: anonymous
Author: Andres Freund
Discussion: https://postgr.es/m/16038-5c974541f2bf6749@postgresql.org
Backpatch: 12, where the bug was introduced in c2fe139c20
2019-10-09 22:00:50 -07:00
Tom Lane db43831899 Avoid using INFO elevel for what are fundamentally debug messages.
Commit 6f6b99d13 stuck an INFO message into the fast path for
checking partition constraints, for no very good reason except
that it made it easy for the regression tests to verify that
that path was taken.  Assorted later patches did likewise,
increasing the unsuppressable-chatter level from ALTER TABLE
even more.  This isn't good for the user experience, so let's
drop these messages down to DEBUG1 where they belong.  So as
not to have a loss of test coverage, create a TAP test that
runs the relevant queries with client_min_messages = DEBUG1
and greps for the expected messages.

This testing method is a bit brute-force --- in particular,
it duplicates the execution of a fair amount of the core
create_table and alter_table tests.  We experimented with
other solutions, but running any significant amount of
standard testing with client_min_messages = DEBUG1 seems
to have a lot of output-stability pitfalls, cf commits
bbb96c370 and 5655565c0.  Possibly at some point we'll look
into whether we can reduce the amount of test duplication.

Backpatch into v12, because some of these messages are new
in v12 and we don't really want to ship it that way.

Sergei Kornilov

Discussion: https://postgr.es/m/81911511895540@web58j.yandex.ru
Discussion: https://postgr.es/m/4859321552643736@myt5-02b80404fd9e.qloud-c.yandex.net
2019-09-07 19:03:11 -04:00
Tom Lane a0555ddab9 Install dependencies to prevent dropping partition key columns.
The logic in ATExecDropColumn that rejects dropping partition key
columns is quite an inadequate defense, because it doesn't execute
in cases where a column needs to be dropped due to cascade from
something that only the column, not the whole partitioned table,
depends on.  That leaves us with a badly broken partitioned table;
even an attempt to load its relcache entry will fail.

We really need to have explicit pg_depend entries that show that the
column can't be dropped without dropping the whole table.  Hence,
add those entries.  In v12 and HEAD, bump catversion to ensure that
partitioned tables will have such entries.  We can't do that in
released branches of course, so in v10 and v11 this patch affords
protection only to partitioned tables created after the patch is
installed.  Given the lack of field complaints (this bug was found
by fuzz-testing not by end users), that's probably good enough.

In passing, fix ATExecDropColumn and ATPrepAlterColumnType
messages to be more specific about which partition key column
they're complaining about.

Per report from Manuel Rigger.  Back-patch to v10 where partitioned
tables were added.

Discussion: https://postgr.es/m/CA+u7OA4JKCPFrdrAbOs7XBiCyD61XJxeNav4LefkSmBLQ-Vobg@mail.gmail.com
Discussion: https://postgr.es/m/31920.1562526703@sss.pgh.pa.us
2019-07-22 14:55:40 -04:00
Tom Lane 0ab1a2e39b Remove dead encoding-conversion functions.
The code for conversions SQL_ASCII <-> MULE_INTERNAL and
SQL_ASCII <-> UTF8 was unreachable, because we long ago changed
the wrapper functions pg_do_encoding_conversion() et al so that
they have hard-wired behaviors for conversions involving SQL_ASCII.
(At least some of those fast paths date back to 2002, though it
looks like we may not have been totally consistent about this until
later.)  Given the lack of complaints, nobody is dissatisfied with
this state of affairs.  Hence, let's just remove the unreachable code.

Also, change CREATE CONVERSION so that it rejects attempts to
define such conversions.  Since we consider that SQL_ASCII represents
lack of knowledge about the encoding in use, such a conversion would
be semantically dubious even if it were reachable.

Adjust a couple of regression test cases that had randomly decided
to rely on these conversion functions rather than any other ones.

Discussion: https://postgr.es/m/41163.1559156593@sss.pgh.pa.us
2019-07-05 14:17:27 -04:00
Tom Lane 4d6603f28d Simplify psql \d's rule for ordering the indexes of a table.
The previous rule was "primary key (if any) first, then other unique
indexes in name order, then all other indexes in name order".
But the preference for unique indexes seems a bit obsolete since the
introduction of exclusion constraints.   It's no longer the case
that unique indexes are the only ones that constrain what data can
be in the table, and it's hard to see what other rationale there is
for separating out unique indexes.  Other new features like the
possibility for some indexes to be INVALID (hence, not constraining
anything) make this even shakier.

Hence, simplify the sort order to be "primary key (if any) first,
then all other indexes in name order".

No documentation change, since this was never documented anyway.
A couple of existing regression test cases change output, though.

Discussion: https://postgr.es/m/14422.1561474929@sss.pgh.pa.us
2019-07-02 12:32:49 -04:00
Alvaro Herrera 23cccb17fe Fix for dropped columns in a partitioned table's default partition
We forgot to map column numbers to/from the default partition for
various operations, leading to valid cases failing with spurious
errors, such as
ERROR:  attribute N of type some_partition has been dropped

It was also possible that the search for conflicting rows in the default
partition when attaching another partition would fail to detect some.
Secondarily, it was also possible that such a search should be skipped
(because the constraint was implied) but wasn't.

Fix all this by mapping column numbers when necessary.

Reported by: Daniel Wilches
Author: Amit Langote
Discussion: https://postgr.es/m/15873-8c61945d6b3ef87c@postgresql.org
2019-06-28 14:51:08 -04:00
Tom Lane f946a40914 Further fix ALTER COLUMN TYPE's handling of indexes and index constraints.
This patch reverts all the code changes of commit e76de8861, which turns
out to have been seriously misguided.  We can't wait till later to compute
the definition string for an index; we must capture that before applying
the data type change for any column it depends on, else ruleutils.c will
deliverr wrong/misleading results.  (This fine point was documented
nowhere, of course.)

I'd also managed to forget that ATExecAlterColumnType executes once per
ALTER COLUMN TYPE clause, not once per statement; which resulted in the
code being basically completely broken for any case in which multiple ALTER
COLUMN TYPE clauses are applied to a table having non-constraint indexes
that must be rebuilt.  Through very bad luck, none of the existing test
cases nor the ones added by e76de8861 caught that, but of course it was
soon found in the field.

The previous patch also had an implicit assumption that if a constraint's
index had a dependency on a table column, so would the constraint --- but
that isn't actually true, so it didn't fix such cases.

Instead of trying to delete unneeded index dependencies later, do the
is-there-a-constraint lookup immediately on seeing an index dependency,
and switch to remembering the constraint if so.  In the unusual case of
multiple column dependencies for a constraint index, this will result in
duplicate constraint lookups, but that's not that horrible compared to all
the other work that happens here.  Besides, such cases did not work at all
before, so it's hard to argue that they're performance-critical for anyone.

Per bug #15865 from Keith Fiske.  As before, back-patch to all supported
branches.

Discussion: https://postgr.es/m/15865-17940eacc8f8b081@postgresql.org
2019-06-24 16:43:21 -04:00
Tom Lane e76de88615 Fix ALTER COLUMN TYPE failure with a partial exclusion constraint.
ATExecAlterColumnType failed to consider the possibility that an index
that needs to be rebuilt might be a child of a constraint that needs to be
rebuilt.  We missed this so far because usually a constraint index doesn't
have a direct dependency on its table, just on the constraint object.
But if there's a WHERE clause, then dependency analysis of the WHERE
clause results in direct dependencies on the column(s) mentioned in WHERE.
This led to trying to drop and rebuild both the constraint and its
underlying index.

In v11/HEAD, we successfully drop both the index and the constraint,
and then try to rebuild both, and of course the second rebuild hits a
duplicate-index-name problem.  Before v11, it fails with obscure messages
about a missing relation OID, due to trying to drop the index twice.

This is essentially the same kind of problem noted in commit
20bef2c31: the possible dependency linkages are broader than what
ATExecAlterColumnType was designed for.  It was probably OK when
written, but it's certainly been broken since the introduction of
partial exclusion constraints.  Fix by adding an explicit check
for whether any of the indexes-to-be-rebuilt belong to any of the
constraints-to-be-rebuilt, and ignoring any that do.

In passing, fix a latent bug introduced by commit 8b08f7d48: in
get_constraint_index() we must "continue" not "break" when rejecting
a relation of a wrong relkind.  This is harmless today because we don't
expect that code path to be taken anyway; but if there ever were any
relations to be ignored, the existing coding would have an extremely
undesirable dependency on the order of pg_depend entries.

Also adjust a couple of obsolete comments.

Per bug #15835 from Yaroslav Schekin.  Back-patch to all supported
branches.

Discussion: https://postgr.es/m/15835-32d9b7a76c06a7a9@postgresql.org
2019-06-12 12:29:39 -04:00
Noah Misch f2c71cb71f Stop using spelling "nonexistant".
The documentation used "nonexistent" exclusively, and the source tree
used it three times as often as "nonexistant".
2019-06-08 10:12:26 -07:00
Tom Lane c01eb619a8 Apply stopgap fix for bug #15672.
Fix DefineIndex so that it doesn't attempt to pass down a to-be-reused
index relfilenode to a child index creation, and fix TryReuseIndex
to not think that reuse is sensible for a partitioned index.

In v11, this fixes a problem where ALTER TABLE on a partitioned table
could assign the same relfilenode to several different child indexes,
causing very nasty catalog corruption --- in fact, attempting to DROP
the partitioned table then leads not only to a database crash, but to
inability to restart because the same crash will recur during WAL replay.

Either of these two changes would be enough to prevent the failure, but
since neither action could possibly be sane, let's put in both changes
for future-proofing.

In HEAD, no such bug manifests, but that's just an accidental consequence
of having changed the pg_class representation of partitioned indexes to
have relfilenode = 0.  Both of these changes still seem like smart
future-proofing.

This is only a stop-gap because the code for ALTER TABLE on a partitioned
table with a no-op type change still leaves a great deal to be desired.
As the added regression tests show, it gets things wrong for comments on
child indexes/constraints, and it is regenerating child indexes it doesn't
have to.  However, fixing those problems will take more work which may not
get back-patched into v11.  We need a fix for the corruption problem now.

Per bug #15672 from Jianing Yang.

Patch by me, regression test cases based on work by Amit Langote,
who also did a lot of the investigative work.

Discussion: https://postgr.es/m/15672-b9fa7db32698269f@postgresql.org
2019-04-26 17:18:07 -04:00
Tom Lane f4a3fdfbdc Avoid order-of-execution problems with ALTER TABLE ADD PRIMARY KEY.
Up to now, DefineIndex() was responsible for adding attnotnull constraints
to the columns of a primary key, in any case where it hadn't been
convenient for transformIndexConstraint() to mark those columns as
is_not_null.  It (or rather its minion index_check_primary_key) did this
by executing an ALTER TABLE SET NOT NULL command for the target table.

The trouble with this solution is that if we're creating the index due
to ALTER TABLE ADD PRIMARY KEY, and the outer ALTER TABLE has additional
sub-commands, the inner ALTER TABLE's operations executed at the wrong
time with respect to the outer ALTER TABLE's operations.  In particular,
the inner ALTER would perform a validation scan at a point where the
table's storage might be inconsistent with its catalog entries.  (This is
on the hairy edge of being a security problem, but AFAICS it isn't one
because the inner scan would only be interested in the tuples' null
bitmaps.)  This can result in unexpected failures, such as the one seen
in bug #15580 from Allison Kaptur.

To fix, let's remove the attempt to do SET NOT NULL from DefineIndex(),
reducing index_check_primary_key's role to verifying that the columns are
already not null.  (It shouldn't ever see such a case, but it seems wise
to keep the check for safety.)  Instead, make transformIndexConstraint()
generate ALTER TABLE SET NOT NULL subcommands to be executed ahead of
the ADD PRIMARY KEY operation in every case where it can't force the
column to be created already-not-null.  This requires only minor surgery
in parse_utilcmd.c, and it makes for a much more satisfying spec for
transformIndexConstraint(): it's no longer having to take it on faith
that someone else will handle addition of NOT NULL constraints.

To make that work, we have to move the execution of AT_SetNotNull into
an ALTER pass that executes ahead of AT_PASS_ADD_INDEX.  I moved it to
AT_PASS_COL_ATTRS, and put that after AT_PASS_ADD_COL to avoid failure
when the column is being added in the same command.  This incidentally
fixes a bug in the only previous usage of AT_PASS_COL_ATTRS, for
AT_SetIdentity: it didn't work either for a newly-added column.

Playing around with this exposed a separate bug in ALTER TABLE ONLY ...
ADD PRIMARY KEY for partitioned tables.  The intent of the ONLY modifier
in that context is to prevent doing anything that would require holding
lock for a long time --- but the implied SET NOT NULL would recurse to
the child partitions, and do an expensive validation scan for any child
where the column(s) were not already NOT NULL.  To fix that, invent a
new ALTER subcommand AT_CheckNotNull that just insists that a child
column be already NOT NULL, and apply that, not AT_SetNotNull, when
recursing to children in this scenario.  This results in a slightly laxer
definition of ALTER TABLE ONLY ... SET NOT NULL for partitioned tables,
too: that command will now work as long as all children are already NOT
NULL, whereas before it just threw up its hands if there were any
partitions.

In passing, clean up the API of generateClonedIndexStmt(): remove a
useless argument, ensure that the output argument is not left undefined,
update the header comment.

A small side effect of this change is that no-such-column errors in ALTER
TABLE ADD PRIMARY KEY now produce a different message that includes the
table name, because they are now detected by the SET NOT NULL step which
has historically worded its error that way.  That seems fine to me, so
I didn't make any effort to avoid the wording change.

The basic bug #15580 is of very long standing, and these other bugs
aren't new in v12 either.  However, this is a pretty significant change
in the way ALTER TABLE ADD PRIMARY KEY works.  On balance it seems best
not to back-patch, at least not till we get some more confidence that
this patch has no new bugs.

Patch by me, but thanks to Jie Zhang for a preliminary version.

Discussion: https://postgr.es/m/15580-d1a6de5a3d65da51@postgresql.org
Discussion: https://postgr.es/m/1396E95157071C4EBBA51892C5368521017F2E6E63@G08CNEXMBPEKD02.g08.fujitsu.local
2019-04-23 12:25:27 -04:00
Robert Haas 5655565c07 Revert setting client_min_messages to 'debug1' in new tests.
The buildfarm doesn't like this, because some buildfarm members have
log_statement = 'all'.  We could change the log level of the messages
instead, but Tom doesn't like that.  So let's do this instead, at
least for now.

Patch by Sergei Kornilov, applied here in reverse.

Discussion: http://postgr.es/m/2123251552490241@myt6-fe24916a5562.qloud-c.yandex.net
2019-03-13 13:18:25 -04:00
Peter Eisentraut f177660ab0 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 14:25:42 +01:00
Robert Haas bbb96c3704 Allow ALTER TABLE .. SET NOT NULL to skip provably unnecessary scans.
If existing CHECK or NOT NULL constraints preclude the presence
of nulls, we need not look to see whether any are present.

Sergei Kornilov, reviewed by Stephen Frost, Ildar Musin, David Rowley,
and by me.

Discussion: http://postgr.es/m/81911511895540@web58j.yandex.ru
2019-03-13 08:55:00 -04:00
Thomas Munro 91595f9d49 Drop the vestigial "smgr" type.
Before commit 3fa2bb31 this type appeared in the catalogs to
select which of several block storage mechanisms each relation
used.

New features under development propose to revive the concept of
different block storage managers for new kinds of data accessed
via bufmgr.c, but don't need to put references to them in the
catalogs.  So, avoid useless maintenance work on this type by
dropping it.  Update some regression tests that were referencing
it where any type would do.

Discussion: https://postgr.es/m/CA%2BhUKG%2BDE0mmiBZMtZyvwWtgv1sZCniSVhXYsXkvJ_Wo%2B83vvw%40mail.gmail.com
2019-03-07 15:44:04 +13:00
Tom Lane 1fb57af920 Create the infrastructure for planner support functions.
Rename/repurpose pg_proc.protransform as "prosupport".  The idea is
still that it names an internal function that provides knowledge to
the planner about the behavior of the function it's attached to;
but redesign the API specification so that it's not limited to doing
just one thing, but can support an extensible set of requests.

The original purpose of simplifying a function call is handled by
the first request type to be invented, SupportRequestSimplify.
Adjust all the existing transform functions to handle this API,
and rename them fron "xxx_transform" to "xxx_support" to reflect
the potential generalization of what they do.  (Since we never
previously provided any way for extensions to add transform functions,
this change doesn't create an API break for them.)

Also add DDL and pg_dump support for attaching a support function to a
user-defined function.  Unfortunately, DDL access has to be restricted
to superusers, at least for now; but seeing that support functions
will pretty much have to be written in C, that limitation is just
theoretical.  (This support is untested in this patch, but a follow-on
patch will add cases that exercise it.)

Discussion: https://postgr.es/m/15193.1548028093@sss.pgh.pa.us
2019-02-09 18:08:48 -05:00
Tom Lane f1ad067fc3 Sort the dependent objects before recursing in findDependentObjects().
Historically, the notices output by DROP CASCADE tended to come out
in uncertain order, and in some cases you might get different claims
about which object depends on which other one.  This is because we
just traversed the dependency tree in the order in which pg_depend
entries are seen, and nbtree has never promised anything about the
order of equal-keyed index entries.  We've put up with that for years,
hacking regression tests when necessary to prevent them from emitting
unstable output.  However, it's a problem for pending work that will
change nbtree's behavior for equal keys, as that causes unexpected
changes in the regression test results.

Hence, adjust findDependentObjects to sort the results of each
indexscan before processing them.  The sort is on descending OID of
the dependent objects, hence more or less reverse creation order.
While this rule could still result in bogus regression test failures
if an OID wraparound occurred mid-test, that seems unlikely to happen
in any plausible development or packaging-test scenario.

This is enough to ensure output stability for ordinary DROP CASCADE
commands, but not for DROP OWNED BY, because that has a different
code path with the same problem.  We might later choose to sort in
the DROP OWNED BY code as well, but this patch doesn't do so.

I've also not done anything about reverting the existing hacks to
suppress unstable DROP CASCADE output in specific regression tests.
It might be worth undoing those, but it seems like a distinct question.

The first indexscan loop in findDependentObjects is not touched,
meaning there is a hazard of unstable error reports from that too.
However, said hazard is not the fault of that code: it was designed
on the assumption that there could be at most one "owning" object
to complain about, and that assumption does not seem unreasonable.
The recent patch that added the possibility of multiple
DEPENDENCY_INTERNAL_AUTO links broke that assumption, but we should
fix that situation not band-aid around it.  That's a matter for
another patch, though.

Discussion: https://postgr.es/m/12244.1547854440@sss.pgh.pa.us
2019-01-21 13:48:14 -05:00