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postgresql/src/backend/catalog/pg_inherits.c

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Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
/*-------------------------------------------------------------------------
*
* pg_inherits.c
* routines to support manipulation of the pg_inherits relation
*
Disallow converting an inheritance child table to a view. Generally, members of inheritance trees must be plain tables (or, in more recent versions, foreign tables). ALTER TABLE INHERIT rejects creating an inheritance relationship that has a view at either end. When DefineQueryRewrite attempts to convert a relation to a view, it already had checks prohibiting doing so for partitioning parents or children as well as traditional-inheritance parents ... but it neglected to check that a traditional-inheritance child wasn't being converted. Since the planner assumes that any inheritance child is a table, this led to making plans that tried to do a physical scan on a view, causing failures (or even crashes, in recent versions). One could imagine trying to support such a case by expanding the view normally, but since the rewriter runs before the planner does inheritance expansion, it would take some very fundamental refactoring to make that possible. There are probably a lot of other parts of the system that don't cope well with such a situation, too. For now, just forbid it. Per bug #16856 from Yang Lin. Back-patch to all supported branches. (In versions before v10, this includes back-patching the portion of commit 501ed02cf that added has_superclass(). Perhaps the lack of that infrastructure partially explains the missing check.) Discussion: https://postgr.es/m/16856-0363e05c6e1612fd@postgresql.org
2021-02-06 21:17:01 +01:00
* Note: currently, this module mostly contains inquiry functions; actual
* creation and deletion of pg_inherits entries is mostly done in tablecmds.c.
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
* Perhaps someday that code should be moved here, but it'd have to be
* disentangled from other stuff such as pg_depend updates.
*
Update copyright for 2021 Backpatch-through: 9.5
2021-01-02 19:06:25 +01:00
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
Remove cvs keywords from all files.
2010-09-20 22:08:53 +02:00
* src/backend/catalog/pg_inherits.c
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
Revert "Rename files and headers related to index AM" This follows multiple complains from Peter Geoghegan, Andres Freund and Alvaro Herrera that this issue ought to be dug more before actually happening, if it happens. Discussion: https://postgr.es/m/20191226144606.GA5659@alvherre.pgsql
2019-12-27 00:09:00 +01:00
#include "access/genam.h"
Split tuple struct defs from htup.h to htup_details.h This reduces unnecessary exposure of other headers through htup.h, which is very widely included by many files. I have chosen to move the function prototypes to the new file as well, because that means htup.h no longer needs to include tupdesc.h. In itself this doesn't have much effect in indirect inclusion of tupdesc.h throughout the tree, because it's also required by execnodes.h; but it's something to explore in the future, and it seemed best to do the htup.h change now while I'm busy with it.
2012-08-30 22:15:44 +02:00
#include "access/htup_details.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/table.h"
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
#include "catalog/indexing.h"
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
#include "catalog/pg_inherits.h"
#include "parser/parse_type.h"
Modify find_inheritance_children() and find_all_inheritors() to add the ability to lock relations as they scan pg_inherits, and to ignore any relations that have disappeared by the time we get lock on them. This makes uses of these functions safe against concurrent DROP operations on child tables: we will effectively ignore any just-dropped child, rather than possibly throwing an error as in recent bug report from Thomas Johansson (and similar past complaints). The behavior should not change otherwise, since the code was acquiring those same locks anyway, just a little bit later. An exception is LockTableCommand(), which is still behaving unsafely; but that seems to require some more discussion before we change it.
2009-05-12 05:11:02 +02:00
#include "storage/lmgr.h"
Collect duplicate copies of oid_cmp()
2017-03-01 17:55:28 +01:00
#include "utils/builtins.h"
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
#include "utils/fmgroids.h"
Fix leakage of memory context header in find_all_inheritors(). Commit 827d6f977 contained the same misunderstanding of hash_create's API as commit 090010f2e. As in 5d00b764c, remove the unnecessary layer of memory context. (This bug is less significant than the other one, since the extra context would be under a relatively short-lived context, but it's still a bug.)
2017-05-17 01:33:31 +02:00
#include "utils/memutils.h"
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 22:00:28 +01:00
#include "utils/snapmgr.h"
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
#include "utils/syscache.h"
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
/*
* Entry of a hash table used in find_all_inheritors. See below.
*/
typedef struct SeenRelsEntry
{
Oid rel_id; /* relation oid */
Represent Lists as expansible arrays, not chains of cons-cells. Originally, Postgres Lists were a more or less exact reimplementation of Lisp lists, which consist of chains of separately-allocated cons cells, each having a value and a next-cell link. We'd hacked that once before (commit d0b4399d8) to add a separate List header, but the data was still in cons cells. That makes some operations -- notably list_nth() -- O(N), and it's bulky because of the next-cell pointers and per-cell palloc overhead, and it's very cache-unfriendly if the cons cells end up scattered around rather than being adjacent. In this rewrite, we still have List headers, but the data is in a resizable array of values, with no next-cell links. Now we need at most two palloc's per List, and often only one, since we can allocate some values in the same palloc call as the List header. (Of course, extending an existing List may require repalloc's to enlarge the array. But this involves just O(log N) allocations not O(N).) Of course this is not without downsides. The key difficulty is that addition or deletion of a list entry may now cause other entries to move, which it did not before. For example, that breaks foreach() and sister macros, which historically used a pointer to the current cons-cell as loop state. We can repair those macros transparently by making their actual loop state be an integer list index; the exposed "ListCell *" pointer is no longer state carried across loop iterations, but is just a derived value. (In practice, modern compilers can optimize things back to having just one loop state value, at least for simple cases with inline loop bodies.) In principle, this is a semantics change for cases where the loop body inserts or deletes list entries ahead of the current loop index; but I found no such cases in the Postgres code. The change is not at all transparent for code that doesn't use foreach() but chases lists "by hand" using lnext(). The largest share of such code in the backend is in loops that were maintaining "prev" and "next" variables in addition to the current-cell pointer, in order to delete list cells efficiently using list_delete_cell(). However, we no longer need a previous-cell pointer to delete a list cell efficiently. Keeping a next-cell pointer doesn't work, as explained above, but we can improve matters by changing such code to use a regular foreach() loop and then using the new macro foreach_delete_current() to delete the current cell. (This macro knows how to update the associated foreach loop's state so that no cells will be missed in the traversal.) There remains a nontrivial risk of code assuming that a ListCell * pointer will remain good over an operation that could now move the list contents. To help catch such errors, list.c can be compiled with a new define symbol DEBUG_LIST_MEMORY_USAGE that forcibly moves list contents whenever that could possibly happen. This makes list operations significantly more expensive so it's not normally turned on (though it is on by default if USE_VALGRIND is on). There are two notable API differences from the previous code: * lnext() now requires the List's header pointer in addition to the current cell's address. * list_delete_cell() no longer requires a previous-cell argument. These changes are somewhat unfortunate, but on the other hand code using either function needs inspection to see if it is assuming anything it shouldn't, so it's not all bad. Programmers should be aware of these significant performance changes: * list_nth() and related functions are now O(1); so there's no major access-speed difference between a list and an array. * Inserting or deleting a list element now takes time proportional to the distance to the end of the list, due to moving the array elements. (However, it typically *doesn't* require palloc or pfree, so except in long lists it's probably still faster than before.) Notably, lcons() used to be about the same cost as lappend(), but that's no longer true if the list is long. Code that uses lcons() and list_delete_first() to maintain a stack might usefully be rewritten to push and pop at the end of the list rather than the beginning. * There are now list_insert_nth...() and list_delete_nth...() functions that add or remove a list cell identified by index. These have the data-movement penalty explained above, but there's no search penalty. * list_concat() and variants now copy the second list's data into storage belonging to the first list, so there is no longer any sharing of cells between the input lists. The second argument is now declared "const List *" to reflect that it isn't changed. This patch just does the minimum needed to get the new implementation in place and fix bugs exposed by the regression tests. As suggested by the foregoing, there's a fair amount of followup work remaining to do. Also, the ENABLE_LIST_COMPAT macros are finally removed in this commit. Code using those should have been gone a dozen years ago. Patch by me; thanks to David Rowley, Jesper Pedersen, and others for review. Discussion: https://postgr.es/m/11587.1550975080@sss.pgh.pa.us
2019-07-15 19:41:58 +02:00
int list_index; /* its position in output list(s) */
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
} SeenRelsEntry;
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
/*
* find_inheritance_children
*
* Returns a list containing the OIDs of all relations which
* inherit *directly* from the relation with OID 'parentrelId'.
Modify find_inheritance_children() and find_all_inheritors() to add the ability to lock relations as they scan pg_inherits, and to ignore any relations that have disappeared by the time we get lock on them. This makes uses of these functions safe against concurrent DROP operations on child tables: we will effectively ignore any just-dropped child, rather than possibly throwing an error as in recent bug report from Thomas Johansson (and similar past complaints). The behavior should not change otherwise, since the code was acquiring those same locks anyway, just a little bit later. An exception is LockTableCommand(), which is still behaving unsafely; but that seems to require some more discussion before we change it.
2009-05-12 05:11:02 +02:00
*
* The specified lock type is acquired on each child relation (but not on the
* given rel; caller should already have locked it). If lockmode is NoLock
* then no locks are acquired, but caller must beware of race conditions
* against possible DROPs of child relations.
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 22:00:28 +01:00
*
Allow a partdesc-omitting-partitions to be cached Makes partition descriptor acquisition faster during the transient period in which a partition is in the process of being detached. This also adds the restriction that only one partition can be in pending-detach state for a partitioned table. While at it, return find_inheritance_children() API to what it was before 71f4c8c6f74b, and create a separate find_inheritance_children_extended() that returns detailed info about detached partitions. (This incidentally fixes a bug in 8aba9322511 whereby a memory context holding a transient partdesc is reparented to a NULL PortalContext, leading to permanent leak of that memory. The fix is to no longer rely on reparenting contexts to PortalContext. Reported by Amit Langote.) Per gripe from Amit Langote Discussion: https://postgr.es/m/CA+HiwqFgpP1LxJZOBYGt9rpvTjXXkg5qG2+Xch2Z1Q7KrqZR1A@mail.gmail.com
2021-04-28 21:44:35 +02:00
* Partitions marked as being detached are omitted; see
* find_inheritance_children_extended for details.
*/
List *
find_inheritance_children(Oid parentrelId, LOCKMODE lockmode)
{
return find_inheritance_children_extended(parentrelId, true, lockmode,
NULL, NULL);
}
/*
* find_inheritance_children_extended
*
* As find_inheritance_children, with more options regarding detached
* partitions.
*
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
* If a partition's pg_inherits row is marked "detach pending",
Fix uninitialized memory bug Have interested callers of find_inheritance_children set the detached_exist value to false prior to calling it, so that that routine only has to set it true in the rare cases where it is necessary. Don't touch it otherwise. Per buildfarm member thorntail (which reported a UBSan failure here).
2021-04-22 22:04:48 +02:00
* *detached_exist (if not null) is set true.
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
*
* If omit_detached is true and there is an active snapshot (not the same as
* the catalog snapshot used to scan pg_inherits!) and a pg_inherits tuple
* marked "detach pending" is visible to that snapshot, then that partition is
* omitted from the output list. This makes partitions invisible depending on
* whether the transaction that marked those partitions as detached appears
Allow a partdesc-omitting-partitions to be cached Makes partition descriptor acquisition faster during the transient period in which a partition is in the process of being detached. This also adds the restriction that only one partition can be in pending-detach state for a partitioned table. While at it, return find_inheritance_children() API to what it was before 71f4c8c6f74b, and create a separate find_inheritance_children_extended() that returns detailed info about detached partitions. (This incidentally fixes a bug in 8aba9322511 whereby a memory context holding a transient partdesc is reparented to a NULL PortalContext, leading to permanent leak of that memory. The fix is to no longer rely on reparenting contexts to PortalContext. Reported by Amit Langote.) Per gripe from Amit Langote Discussion: https://postgr.es/m/CA+HiwqFgpP1LxJZOBYGt9rpvTjXXkg5qG2+Xch2Z1Q7KrqZR1A@mail.gmail.com
2021-04-28 21:44:35 +02:00
* committed to the active snapshot. In addition, *detached_xmin (if not null)
* is set to the xmin of the row of the detached partition.
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
*/
List *
Allow a partdesc-omitting-partitions to be cached Makes partition descriptor acquisition faster during the transient period in which a partition is in the process of being detached. This also adds the restriction that only one partition can be in pending-detach state for a partitioned table. While at it, return find_inheritance_children() API to what it was before 71f4c8c6f74b, and create a separate find_inheritance_children_extended() that returns detailed info about detached partitions. (This incidentally fixes a bug in 8aba9322511 whereby a memory context holding a transient partdesc is reparented to a NULL PortalContext, leading to permanent leak of that memory. The fix is to no longer rely on reparenting contexts to PortalContext. Reported by Amit Langote.) Per gripe from Amit Langote Discussion: https://postgr.es/m/CA+HiwqFgpP1LxJZOBYGt9rpvTjXXkg5qG2+Xch2Z1Q7KrqZR1A@mail.gmail.com
2021-04-28 21:44:35 +02:00
find_inheritance_children_extended(Oid parentrelId, bool omit_detached,
LOCKMODE lockmode, bool *detached_exist,
TransactionId *detached_xmin)
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
{
List *list = NIL;
Relation relation;
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
SysScanDesc scan;
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
ScanKeyData key[1];
HeapTuple inheritsTuple;
Oid inhrelid;
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
Oid *oidarr;
int maxoids,
numoids,
i;
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
/*
* Can skip the scan if pg_class shows the relation has never had a
* subclass.
*/
if (!has_subclass(parentrelId))
return NIL;
/*
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
* Scan pg_inherits and build a working array of subclass OIDs.
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
*/
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
maxoids = 32;
oidarr = (Oid *) palloc(maxoids * sizeof(Oid));
numoids = 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
relation = table_open(InheritsRelationId, AccessShareLock);
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
ScanKeyInit(&key[0],
Anum_pg_inherits_inhparent,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(parentrelId));
Modify find_inheritance_children() and find_all_inheritors() to add the ability to lock relations as they scan pg_inherits, and to ignore any relations that have disappeared by the time we get lock on them. This makes uses of these functions safe against concurrent DROP operations on child tables: we will effectively ignore any just-dropped child, rather than possibly throwing an error as in recent bug report from Thomas Johansson (and similar past complaints). The behavior should not change otherwise, since the code was acquiring those same locks anyway, just a little bit later. An exception is LockTableCommand(), which is still behaving unsafely; but that seems to require some more discussion before we change it.
2009-05-12 05:11:02 +02:00
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
scan = systable_beginscan(relation, InheritsParentIndexId, true,
Use an MVCC snapshot, rather than SnapshotNow, for catalog scans. SnapshotNow scans have the undesirable property that, in the face of concurrent updates, the scan can fail to see either the old or the new versions of the row. In many cases, we work around this by requiring DDL operations to hold AccessExclusiveLock on the object being modified; in some cases, the existing locking is inadequate and random failures occur as a result. This commit doesn't change anything related to locking, but will hopefully pave the way to allowing lock strength reductions in the future. The major issue has held us back from making this change in the past is that taking an MVCC snapshot is significantly more expensive than using a static special snapshot such as SnapshotNow. However, testing of various worst-case scenarios reveals that this problem is not severe except under fairly extreme workloads. To mitigate those problems, we avoid retaking the MVCC snapshot for each new scan; instead, we take a new snapshot only when invalidation messages have been processed. The catcache machinery already requires that invalidation messages be sent before releasing the related heavyweight lock; else other backends might rely on locally-cached data rather than scanning the catalog at all. Thus, making snapshot reuse dependent on the same guarantees shouldn't break anything that wasn't already subtly broken. Patch by me. Review by Michael Paquier and Andres Freund.
2013-07-02 15:47:01 +02:00
NULL, 1, key);
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
while ((inheritsTuple = systable_getnext(scan)) != NULL)
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
{
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 22:00:28 +01:00
/*
* Cope with partitions concurrently being detached. When we see a
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
* partition marked "detach pending", we omit it from the returned set
* of visible partitions if caller requested that and the tuple's xmin
* does not appear in progress to the active snapshot. (If there's no
* active snapshot set, that means we're not running a user query, so
* it's OK to always include detached partitions in that case; if the
* xmin is still running to the active snapshot, then the partition
* has not been detached yet and so we include it.)
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 22:00:28 +01:00
*
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
* The reason for this hack is that we want to avoid seeing the
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 22:00:28 +01:00
* partition as alive in RI queries during REPEATABLE READ or
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
* SERIALIZABLE transactions: such queries use a different snapshot
* than the one used by regular (user) queries.
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 22:00:28 +01:00
*/
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
if (((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhdetachpending)
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 22:00:28 +01:00
{
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
if (detached_exist)
*detached_exist = true;
if (omit_detached && ActiveSnapshotSet())
{
TransactionId xmin;
Snapshot snap;
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 22:00:28 +01:00
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
xmin = HeapTupleHeaderGetXmin(inheritsTuple->t_data);
snap = GetActiveSnapshot();
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 22:00:28 +01:00
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
if (!XidInMVCCSnapshot(xmin, snap))
Allow a partdesc-omitting-partitions to be cached Makes partition descriptor acquisition faster during the transient period in which a partition is in the process of being detached. This also adds the restriction that only one partition can be in pending-detach state for a partitioned table. While at it, return find_inheritance_children() API to what it was before 71f4c8c6f74b, and create a separate find_inheritance_children_extended() that returns detailed info about detached partitions. (This incidentally fixes a bug in 8aba9322511 whereby a memory context holding a transient partdesc is reparented to a NULL PortalContext, leading to permanent leak of that memory. The fix is to no longer rely on reparenting contexts to PortalContext. Reported by Amit Langote.) Per gripe from Amit Langote Discussion: https://postgr.es/m/CA+HiwqFgpP1LxJZOBYGt9rpvTjXXkg5qG2+Xch2Z1Q7KrqZR1A@mail.gmail.com
2021-04-28 21:44:35 +02:00
{
if (detached_xmin)
{
/*
* Two detached partitions should not occur (see
* checks in MarkInheritDetached), but if they do,
* track the newer of the two. Make sure to warn the
* user, so that they can clean up. Since this is
* just a cross-check against potentially corrupt
* catalogs, we don't make it a full-fledged error
* message.
*/
if (*detached_xmin != InvalidTransactionId)
{
elog(WARNING, "more than one partition pending detach found for table with OID %u",
parentrelId);
if (TransactionIdFollows(xmin, *detached_xmin))
*detached_xmin = xmin;
}
else
*detached_xmin = xmin;
}
/* Don't add the partition to the output list */
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
continue;
Allow a partdesc-omitting-partitions to be cached Makes partition descriptor acquisition faster during the transient period in which a partition is in the process of being detached. This also adds the restriction that only one partition can be in pending-detach state for a partitioned table. While at it, return find_inheritance_children() API to what it was before 71f4c8c6f74b, and create a separate find_inheritance_children_extended() that returns detailed info about detached partitions. (This incidentally fixes a bug in 8aba9322511 whereby a memory context holding a transient partdesc is reparented to a NULL PortalContext, leading to permanent leak of that memory. The fix is to no longer rely on reparenting contexts to PortalContext. Reported by Amit Langote.) Per gripe from Amit Langote Discussion: https://postgr.es/m/CA+HiwqFgpP1LxJZOBYGt9rpvTjXXkg5qG2+Xch2Z1Q7KrqZR1A@mail.gmail.com
2021-04-28 21:44:35 +02:00
}
Fix relcache inconsistency hazard in partition detach During queries coming from ri_triggers.c, we need to omit partitions that are marked pending detach -- otherwise, the RI query is tricked into allowing a row into the referencing table whose corresponding row is in the detached partition. Which is bogus: once the detach operation completes, the row becomes an orphan. However, the code was not doing that in repeatable-read transactions, because relcache kept a copy of the partition descriptor that included the partition, and used it in the RI query. This commit changes the partdesc cache code to only keep descriptors that aren't dependent on a snapshot (namely: those where no detached partition exist, and those where detached partitions are included). When a partdesc-without- detached-partitions is requested, we create one afresh each time; also, those partdescs are stored in PortalContext instead of CacheMemoryContext. find_inheritance_children gets a new output *detached_exist boolean, which indicates whether any partition marked pending-detach is found. Its "include_detached" input flag is changed to "omit_detached", because that name captures desired the semantics more naturally. CreatePartitionDirectory() and RelationGetPartitionDesc() arguments are identically renamed. This was noticed because a buildfarm member that runs with relcache clobbering, which would not keep the improperly cached partdesc, broke one test, which led us to realize that the expected output of that test was bogus. This commit also corrects that expected output. Author: Amit Langote <amitlangote09@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://postgr.es/m/3269784.1617215412@sss.pgh.pa.us
2021-04-22 21:13:25 +02:00
}
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 22:00:28 +01:00
}
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
inhrelid = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhrelid;
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
if (numoids >= maxoids)
{
maxoids *= 2;
oidarr = (Oid *) repalloc(oidarr, maxoids * sizeof(Oid));
}
oidarr[numoids++] = inhrelid;
}
systable_endscan(scan);
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, AccessShareLock);
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
/*
* If we found more than one child, sort them by OID. This ensures
* reasonably consistent behavior regardless of the vagaries of an
* indexscan. This is important since we need to be sure all backends
* lock children in the same order to avoid needless deadlocks.
*/
if (numoids > 1)
qsort(oidarr, numoids, sizeof(Oid), oid_cmp);
/*
* Acquire locks and build the result list.
*/
for (i = 0; i < numoids; i++)
{
inhrelid = oidarr[i];
Modify find_inheritance_children() and find_all_inheritors() to add the ability to lock relations as they scan pg_inherits, and to ignore any relations that have disappeared by the time we get lock on them. This makes uses of these functions safe against concurrent DROP operations on child tables: we will effectively ignore any just-dropped child, rather than possibly throwing an error as in recent bug report from Thomas Johansson (and similar past complaints). The behavior should not change otherwise, since the code was acquiring those same locks anyway, just a little bit later. An exception is LockTableCommand(), which is still behaving unsafely; but that seems to require some more discussion before we change it.
2009-05-12 05:11:02 +02:00
if (lockmode != NoLock)
{
/* Get the lock to synchronize against concurrent drop */
LockRelationOid(inhrelid, lockmode);
/*
* Now that we have the lock, double-check to see if the relation
* really exists or not. If not, assume it was dropped while we
* waited to acquire lock, and ignore it.
*/
Wrap calls to SearchSysCache and related functions using macros. The purpose of this change is to eliminate the need for every caller of SearchSysCache, SearchSysCacheCopy, SearchSysCacheExists, GetSysCacheOid, and SearchSysCacheList to know the maximum number of allowable keys for a syscache entry (currently 4). This will make it far easier to increase the maximum number of keys in a future release should we choose to do so, and it makes the code shorter, too. Design and review by Tom Lane.
2010-02-14 19:42:19 +01:00
if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(inhrelid)))
Modify find_inheritance_children() and find_all_inheritors() to add the ability to lock relations as they scan pg_inherits, and to ignore any relations that have disappeared by the time we get lock on them. This makes uses of these functions safe against concurrent DROP operations on child tables: we will effectively ignore any just-dropped child, rather than possibly throwing an error as in recent bug report from Thomas Johansson (and similar past complaints). The behavior should not change otherwise, since the code was acquiring those same locks anyway, just a little bit later. An exception is LockTableCommand(), which is still behaving unsafely; but that seems to require some more discussion before we change it.
2009-05-12 05:11:02 +02:00
{
/* Release useless lock */
UnlockRelationOid(inhrelid, lockmode);
/* And ignore this relation */
continue;
}
}
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
list = lappend_oid(list, inhrelid);
}
Modify find_inheritance_children() and find_all_inheritors() to add the ability to lock relations as they scan pg_inherits, and to ignore any relations that have disappeared by the time we get lock on them. This makes uses of these functions safe against concurrent DROP operations on child tables: we will effectively ignore any just-dropped child, rather than possibly throwing an error as in recent bug report from Thomas Johansson (and similar past complaints). The behavior should not change otherwise, since the code was acquiring those same locks anyway, just a little bit later. An exception is LockTableCommand(), which is still behaving unsafely; but that seems to require some more discussion before we change it.
2009-05-12 05:11:02 +02:00
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
pfree(oidarr);
Modify find_inheritance_children() and find_all_inheritors() to add the ability to lock relations as they scan pg_inherits, and to ignore any relations that have disappeared by the time we get lock on them. This makes uses of these functions safe against concurrent DROP operations on child tables: we will effectively ignore any just-dropped child, rather than possibly throwing an error as in recent bug report from Thomas Johansson (and similar past complaints). The behavior should not change otherwise, since the code was acquiring those same locks anyway, just a little bit later. An exception is LockTableCommand(), which is still behaving unsafely; but that seems to require some more discussion before we change it.
2009-05-12 05:11:02 +02:00
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
return list;
}
/*
* find_all_inheritors -
* Returns a list of relation OIDs including the given rel plus
* all relations that inherit from it, directly or indirectly.
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
* Optionally, it also returns the number of parents found for
* each such relation within the inheritance tree rooted at the
* given rel.
Modify find_inheritance_children() and find_all_inheritors() to add the ability to lock relations as they scan pg_inherits, and to ignore any relations that have disappeared by the time we get lock on them. This makes uses of these functions safe against concurrent DROP operations on child tables: we will effectively ignore any just-dropped child, rather than possibly throwing an error as in recent bug report from Thomas Johansson (and similar past complaints). The behavior should not change otherwise, since the code was acquiring those same locks anyway, just a little bit later. An exception is LockTableCommand(), which is still behaving unsafely; but that seems to require some more discussion before we change it.
2009-05-12 05:11:02 +02:00
*
* The specified lock type is acquired on all child relations (but not on the
* given rel; caller should already have locked it). If lockmode is NoLock
* then no locks are acquired, but caller must beware of race conditions
* against possible DROPs of child relations.
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 22:00:28 +01:00
*
* NB - No current callers of this routine are interested in children being
* concurrently detached, so there's no provision to include them.
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
*/
List *
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
find_all_inheritors(Oid parentrelId, LOCKMODE lockmode, List **numparents)
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
{
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
/* hash table for O(1) rel_oid -> rel_numparents cell lookup */
HTAB *seen_rels;
HASHCTL ctl;
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
List *rels_list,
*rel_numparents;
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
ListCell *l;
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
ctl.keysize = sizeof(Oid);
ctl.entrysize = sizeof(SeenRelsEntry);
Fix leakage of memory context header in find_all_inheritors(). Commit 827d6f977 contained the same misunderstanding of hash_create's API as commit 090010f2e. As in 5d00b764c, remove the unnecessary layer of memory context. (This bug is less significant than the other one, since the extra context would be under a relatively short-lived context, but it's still a bug.)
2017-05-17 01:33:31 +02:00
ctl.hcxt = CurrentMemoryContext;
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
Fix leakage of memory context header in find_all_inheritors(). Commit 827d6f977 contained the same misunderstanding of hash_create's API as commit 090010f2e. As in 5d00b764c, remove the unnecessary layer of memory context. (This bug is less significant than the other one, since the extra context would be under a relatively short-lived context, but it's still a bug.)
2017-05-17 01:33:31 +02:00
seen_rels = hash_create("find_all_inheritors temporary table",
32, /* start small and extend */
&ctl,
HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
/*
* We build a list starting with the given rel and adding all direct and
* indirect children. We can use a single list as both the record of
* already-found rels and the agenda of rels yet to be scanned for more
* children. This is a bit tricky but works because the foreach() macro
Represent Lists as expansible arrays, not chains of cons-cells. Originally, Postgres Lists were a more or less exact reimplementation of Lisp lists, which consist of chains of separately-allocated cons cells, each having a value and a next-cell link. We'd hacked that once before (commit d0b4399d8) to add a separate List header, but the data was still in cons cells. That makes some operations -- notably list_nth() -- O(N), and it's bulky because of the next-cell pointers and per-cell palloc overhead, and it's very cache-unfriendly if the cons cells end up scattered around rather than being adjacent. In this rewrite, we still have List headers, but the data is in a resizable array of values, with no next-cell links. Now we need at most two palloc's per List, and often only one, since we can allocate some values in the same palloc call as the List header. (Of course, extending an existing List may require repalloc's to enlarge the array. But this involves just O(log N) allocations not O(N).) Of course this is not without downsides. The key difficulty is that addition or deletion of a list entry may now cause other entries to move, which it did not before. For example, that breaks foreach() and sister macros, which historically used a pointer to the current cons-cell as loop state. We can repair those macros transparently by making their actual loop state be an integer list index; the exposed "ListCell *" pointer is no longer state carried across loop iterations, but is just a derived value. (In practice, modern compilers can optimize things back to having just one loop state value, at least for simple cases with inline loop bodies.) In principle, this is a semantics change for cases where the loop body inserts or deletes list entries ahead of the current loop index; but I found no such cases in the Postgres code. The change is not at all transparent for code that doesn't use foreach() but chases lists "by hand" using lnext(). The largest share of such code in the backend is in loops that were maintaining "prev" and "next" variables in addition to the current-cell pointer, in order to delete list cells efficiently using list_delete_cell(). However, we no longer need a previous-cell pointer to delete a list cell efficiently. Keeping a next-cell pointer doesn't work, as explained above, but we can improve matters by changing such code to use a regular foreach() loop and then using the new macro foreach_delete_current() to delete the current cell. (This macro knows how to update the associated foreach loop's state so that no cells will be missed in the traversal.) There remains a nontrivial risk of code assuming that a ListCell * pointer will remain good over an operation that could now move the list contents. To help catch such errors, list.c can be compiled with a new define symbol DEBUG_LIST_MEMORY_USAGE that forcibly moves list contents whenever that could possibly happen. This makes list operations significantly more expensive so it's not normally turned on (though it is on by default if USE_VALGRIND is on). There are two notable API differences from the previous code: * lnext() now requires the List's header pointer in addition to the current cell's address. * list_delete_cell() no longer requires a previous-cell argument. These changes are somewhat unfortunate, but on the other hand code using either function needs inspection to see if it is assuming anything it shouldn't, so it's not all bad. Programmers should be aware of these significant performance changes: * list_nth() and related functions are now O(1); so there's no major access-speed difference between a list and an array. * Inserting or deleting a list element now takes time proportional to the distance to the end of the list, due to moving the array elements. (However, it typically *doesn't* require palloc or pfree, so except in long lists it's probably still faster than before.) Notably, lcons() used to be about the same cost as lappend(), but that's no longer true if the list is long. Code that uses lcons() and list_delete_first() to maintain a stack might usefully be rewritten to push and pop at the end of the list rather than the beginning. * There are now list_insert_nth...() and list_delete_nth...() functions that add or remove a list cell identified by index. These have the data-movement penalty explained above, but there's no search penalty. * list_concat() and variants now copy the second list's data into storage belonging to the first list, so there is no longer any sharing of cells between the input lists. The second argument is now declared "const List *" to reflect that it isn't changed. This patch just does the minimum needed to get the new implementation in place and fix bugs exposed by the regression tests. As suggested by the foregoing, there's a fair amount of followup work remaining to do. Also, the ENABLE_LIST_COMPAT macros are finally removed in this commit. Code using those should have been gone a dozen years ago. Patch by me; thanks to David Rowley, Jesper Pedersen, and others for review. Discussion: https://postgr.es/m/11587.1550975080@sss.pgh.pa.us
2019-07-15 19:41:58 +02:00
* doesn't fetch the next list element until the bottom of the loop. Note
* that we can't keep pointers into the output lists; but an index is
* sufficient.
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
*/
rels_list = list_make1_oid(parentrelId);
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
rel_numparents = list_make1_int(0);
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
foreach(l, rels_list)
{
Oid currentrel = lfirst_oid(l);
List *currentchildren;
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
ListCell *lc;
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
/* Get the direct children of this rel */
Allow a partdesc-omitting-partitions to be cached Makes partition descriptor acquisition faster during the transient period in which a partition is in the process of being detached. This also adds the restriction that only one partition can be in pending-detach state for a partitioned table. While at it, return find_inheritance_children() API to what it was before 71f4c8c6f74b, and create a separate find_inheritance_children_extended() that returns detailed info about detached partitions. (This incidentally fixes a bug in 8aba9322511 whereby a memory context holding a transient partdesc is reparented to a NULL PortalContext, leading to permanent leak of that memory. The fix is to no longer rely on reparenting contexts to PortalContext. Reported by Amit Langote.) Per gripe from Amit Langote Discussion: https://postgr.es/m/CA+HiwqFgpP1LxJZOBYGt9rpvTjXXkg5qG2+Xch2Z1Q7KrqZR1A@mail.gmail.com
2021-04-28 21:44:35 +02:00
currentchildren = find_inheritance_children(currentrel, lockmode);
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
/*
* Add to the queue only those children not already seen. This avoids
* making duplicate entries in case of multiple inheritance paths from
* the same parent. (It'll also keep us from getting into an infinite
* loop, though theoretically there can't be any cycles in the
* inheritance graph anyway.)
*/
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
foreach(lc, currentchildren)
{
Oid child_oid = lfirst_oid(lc);
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
bool found;
SeenRelsEntry *hash_entry;
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
hash_entry = hash_search(seen_rels, &child_oid, HASH_ENTER, &found);
if (found)
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
{
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
/* if the rel is already there, bump number-of-parents counter */
Represent Lists as expansible arrays, not chains of cons-cells. Originally, Postgres Lists were a more or less exact reimplementation of Lisp lists, which consist of chains of separately-allocated cons cells, each having a value and a next-cell link. We'd hacked that once before (commit d0b4399d8) to add a separate List header, but the data was still in cons cells. That makes some operations -- notably list_nth() -- O(N), and it's bulky because of the next-cell pointers and per-cell palloc overhead, and it's very cache-unfriendly if the cons cells end up scattered around rather than being adjacent. In this rewrite, we still have List headers, but the data is in a resizable array of values, with no next-cell links. Now we need at most two palloc's per List, and often only one, since we can allocate some values in the same palloc call as the List header. (Of course, extending an existing List may require repalloc's to enlarge the array. But this involves just O(log N) allocations not O(N).) Of course this is not without downsides. The key difficulty is that addition or deletion of a list entry may now cause other entries to move, which it did not before. For example, that breaks foreach() and sister macros, which historically used a pointer to the current cons-cell as loop state. We can repair those macros transparently by making their actual loop state be an integer list index; the exposed "ListCell *" pointer is no longer state carried across loop iterations, but is just a derived value. (In practice, modern compilers can optimize things back to having just one loop state value, at least for simple cases with inline loop bodies.) In principle, this is a semantics change for cases where the loop body inserts or deletes list entries ahead of the current loop index; but I found no such cases in the Postgres code. The change is not at all transparent for code that doesn't use foreach() but chases lists "by hand" using lnext(). The largest share of such code in the backend is in loops that were maintaining "prev" and "next" variables in addition to the current-cell pointer, in order to delete list cells efficiently using list_delete_cell(). However, we no longer need a previous-cell pointer to delete a list cell efficiently. Keeping a next-cell pointer doesn't work, as explained above, but we can improve matters by changing such code to use a regular foreach() loop and then using the new macro foreach_delete_current() to delete the current cell. (This macro knows how to update the associated foreach loop's state so that no cells will be missed in the traversal.) There remains a nontrivial risk of code assuming that a ListCell * pointer will remain good over an operation that could now move the list contents. To help catch such errors, list.c can be compiled with a new define symbol DEBUG_LIST_MEMORY_USAGE that forcibly moves list contents whenever that could possibly happen. This makes list operations significantly more expensive so it's not normally turned on (though it is on by default if USE_VALGRIND is on). There are two notable API differences from the previous code: * lnext() now requires the List's header pointer in addition to the current cell's address. * list_delete_cell() no longer requires a previous-cell argument. These changes are somewhat unfortunate, but on the other hand code using either function needs inspection to see if it is assuming anything it shouldn't, so it's not all bad. Programmers should be aware of these significant performance changes: * list_nth() and related functions are now O(1); so there's no major access-speed difference between a list and an array. * Inserting or deleting a list element now takes time proportional to the distance to the end of the list, due to moving the array elements. (However, it typically *doesn't* require palloc or pfree, so except in long lists it's probably still faster than before.) Notably, lcons() used to be about the same cost as lappend(), but that's no longer true if the list is long. Code that uses lcons() and list_delete_first() to maintain a stack might usefully be rewritten to push and pop at the end of the list rather than the beginning. * There are now list_insert_nth...() and list_delete_nth...() functions that add or remove a list cell identified by index. These have the data-movement penalty explained above, but there's no search penalty. * list_concat() and variants now copy the second list's data into storage belonging to the first list, so there is no longer any sharing of cells between the input lists. The second argument is now declared "const List *" to reflect that it isn't changed. This patch just does the minimum needed to get the new implementation in place and fix bugs exposed by the regression tests. As suggested by the foregoing, there's a fair amount of followup work remaining to do. Also, the ENABLE_LIST_COMPAT macros are finally removed in this commit. Code using those should have been gone a dozen years ago. Patch by me; thanks to David Rowley, Jesper Pedersen, and others for review. Discussion: https://postgr.es/m/11587.1550975080@sss.pgh.pa.us
2019-07-15 19:41:58 +02:00
ListCell *numparents_cell;
numparents_cell = list_nth_cell(rel_numparents,
hash_entry->list_index);
lfirst_int(numparents_cell)++;
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
}
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
else
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
{
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
/* if it's not there, add it. expect 1 parent, initially. */
Represent Lists as expansible arrays, not chains of cons-cells. Originally, Postgres Lists were a more or less exact reimplementation of Lisp lists, which consist of chains of separately-allocated cons cells, each having a value and a next-cell link. We'd hacked that once before (commit d0b4399d8) to add a separate List header, but the data was still in cons cells. That makes some operations -- notably list_nth() -- O(N), and it's bulky because of the next-cell pointers and per-cell palloc overhead, and it's very cache-unfriendly if the cons cells end up scattered around rather than being adjacent. In this rewrite, we still have List headers, but the data is in a resizable array of values, with no next-cell links. Now we need at most two palloc's per List, and often only one, since we can allocate some values in the same palloc call as the List header. (Of course, extending an existing List may require repalloc's to enlarge the array. But this involves just O(log N) allocations not O(N).) Of course this is not without downsides. The key difficulty is that addition or deletion of a list entry may now cause other entries to move, which it did not before. For example, that breaks foreach() and sister macros, which historically used a pointer to the current cons-cell as loop state. We can repair those macros transparently by making their actual loop state be an integer list index; the exposed "ListCell *" pointer is no longer state carried across loop iterations, but is just a derived value. (In practice, modern compilers can optimize things back to having just one loop state value, at least for simple cases with inline loop bodies.) In principle, this is a semantics change for cases where the loop body inserts or deletes list entries ahead of the current loop index; but I found no such cases in the Postgres code. The change is not at all transparent for code that doesn't use foreach() but chases lists "by hand" using lnext(). The largest share of such code in the backend is in loops that were maintaining "prev" and "next" variables in addition to the current-cell pointer, in order to delete list cells efficiently using list_delete_cell(). However, we no longer need a previous-cell pointer to delete a list cell efficiently. Keeping a next-cell pointer doesn't work, as explained above, but we can improve matters by changing such code to use a regular foreach() loop and then using the new macro foreach_delete_current() to delete the current cell. (This macro knows how to update the associated foreach loop's state so that no cells will be missed in the traversal.) There remains a nontrivial risk of code assuming that a ListCell * pointer will remain good over an operation that could now move the list contents. To help catch such errors, list.c can be compiled with a new define symbol DEBUG_LIST_MEMORY_USAGE that forcibly moves list contents whenever that could possibly happen. This makes list operations significantly more expensive so it's not normally turned on (though it is on by default if USE_VALGRIND is on). There are two notable API differences from the previous code: * lnext() now requires the List's header pointer in addition to the current cell's address. * list_delete_cell() no longer requires a previous-cell argument. These changes are somewhat unfortunate, but on the other hand code using either function needs inspection to see if it is assuming anything it shouldn't, so it's not all bad. Programmers should be aware of these significant performance changes: * list_nth() and related functions are now O(1); so there's no major access-speed difference between a list and an array. * Inserting or deleting a list element now takes time proportional to the distance to the end of the list, due to moving the array elements. (However, it typically *doesn't* require palloc or pfree, so except in long lists it's probably still faster than before.) Notably, lcons() used to be about the same cost as lappend(), but that's no longer true if the list is long. Code that uses lcons() and list_delete_first() to maintain a stack might usefully be rewritten to push and pop at the end of the list rather than the beginning. * There are now list_insert_nth...() and list_delete_nth...() functions that add or remove a list cell identified by index. These have the data-movement penalty explained above, but there's no search penalty. * list_concat() and variants now copy the second list's data into storage belonging to the first list, so there is no longer any sharing of cells between the input lists. The second argument is now declared "const List *" to reflect that it isn't changed. This patch just does the minimum needed to get the new implementation in place and fix bugs exposed by the regression tests. As suggested by the foregoing, there's a fair amount of followup work remaining to do. Also, the ENABLE_LIST_COMPAT macros are finally removed in this commit. Code using those should have been gone a dozen years ago. Patch by me; thanks to David Rowley, Jesper Pedersen, and others for review. Discussion: https://postgr.es/m/11587.1550975080@sss.pgh.pa.us
2019-07-15 19:41:58 +02:00
hash_entry->list_index = list_length(rels_list);
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
rels_list = lappend_oid(rels_list, child_oid);
rel_numparents = lappend_int(rel_numparents, 1);
}
}
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
}
Tighten integrity checks on ALTER TABLE ... ALTER COLUMN ... RENAME. When a column is renamed, we recursively rename the same column in all descendent tables. But if one of those tables also inherits that column from a table outside the inheritance hierarchy rooted at the named table, we must throw an error. The previous coding correctly prohibited the rename when the parent had inherited the column from elsewhere, but overlooked the case where the parent was OK but a child table also inherited the same column from a second, unrelated parent. For now, not backpatched due to lack of complaints from the field. KaiGai Kohei, with further changes by me. Reviewed by Bernd Helme and Tom Lane.
2010-02-01 20:28:56 +01:00
if (numparents)
*numparents = rel_numparents;
else
list_free(rel_numparents);
Improve performance of find_all_inheritors() Previous coding uses three nested loops which obviously were a pain for large number of table's children. Patch replaces inner loop with a hashmap. Author: Aleksander Alekseev Reviewed-by: me https://commitfest.postgresql.org/13/1058/
2017-03-27 18:07:48 +02:00
hash_destroy(seen_rels);
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
return rels_list;
}
/*
* has_subclass - does this relation have any children?
*
* In the current implementation, has_subclass returns whether a
* particular class *might* have a subclass. It will not return the
* correct result if a class had a subclass which was later dropped.
Teach ANALYZE to clear pg_class.relhassubclass when appropriate. In the past, relhassubclass always remained true if a relation had ever had child relations, even if the last subclass was long gone. While this had only marginal performance implications in most cases, it was annoying, and I'm now considering some planner changes that would raise the cost of a false positive. It was previously impractical to fix this because of race condition concerns. However, given the recent change that made tablecmds.c take ShareExclusiveLock on relations that are gaining a child (commit fbcf4b92aa64d4577bcf25925b055316b978744a), we can now allow ANALYZE to clear the flag when it's no longer relevant. There is no additional locking cost to do so, since ANALYZE takes ShareExclusiveLock anyway.
2011-09-02 20:29:31 +02:00
* This is because relhassubclass in pg_class is not updated immediately
* when a subclass is dropped, primarily because of concurrency concerns.
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
*
* Currently has_subclass is only used as an efficiency hack to skip
Teach ANALYZE to clear pg_class.relhassubclass when appropriate. In the past, relhassubclass always remained true if a relation had ever had child relations, even if the last subclass was long gone. While this had only marginal performance implications in most cases, it was annoying, and I'm now considering some planner changes that would raise the cost of a false positive. It was previously impractical to fix this because of race condition concerns. However, given the recent change that made tablecmds.c take ShareExclusiveLock on relations that are gaining a child (commit fbcf4b92aa64d4577bcf25925b055316b978744a), we can now allow ANALYZE to clear the flag when it's no longer relevant. There is no additional locking cost to do so, since ANALYZE takes ShareExclusiveLock anyway.
2011-09-02 20:29:31 +02:00
* unnecessary inheritance searches, so this is OK. Note that ANALYZE
* on a childless table will clean up the obsolete relhassubclass flag.
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
*
* Although this doesn't actually touch pg_inherits, it seems reasonable
* to keep it here since it's normally used with the other routines here.
*/
bool
has_subclass(Oid relationId)
{
HeapTuple tuple;
bool result;
Wrap calls to SearchSysCache and related functions using macros. The purpose of this change is to eliminate the need for every caller of SearchSysCache, SearchSysCacheCopy, SearchSysCacheExists, GetSysCacheOid, and SearchSysCacheList to know the maximum number of allowable keys for a syscache entry (currently 4). This will make it far easier to increase the maximum number of keys in a future release should we choose to do so, and it makes the code shorter, too. Design and review by Tom Lane.
2010-02-14 19:42:19 +01:00
tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relationId));
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for relation %u", relationId);
result = ((Form_pg_class) GETSTRUCT(tuple))->relhassubclass;
ReleaseSysCache(tuple);
return result;
}
Fix transition tables for partition/inheritance. We disallow row-level triggers with transition tables on child tables. Transition tables for triggers on the parent table contain only those columns present in the parent. (We can't mix tuple formats in a single transition table.) Patch by Thomas Munro Discussion: https://postgr.es/m/CA%2BTgmoZzTBBAsEUh4MazAN7ga%3D8SsMC-Knp-6cetts9yNZUCcg%40mail.gmail.com
2017-06-28 19:55:03 +02:00
/*
Disallow converting an inheritance child table to a view. Generally, members of inheritance trees must be plain tables (or, in more recent versions, foreign tables). ALTER TABLE INHERIT rejects creating an inheritance relationship that has a view at either end. When DefineQueryRewrite attempts to convert a relation to a view, it already had checks prohibiting doing so for partitioning parents or children as well as traditional-inheritance parents ... but it neglected to check that a traditional-inheritance child wasn't being converted. Since the planner assumes that any inheritance child is a table, this led to making plans that tried to do a physical scan on a view, causing failures (or even crashes, in recent versions). One could imagine trying to support such a case by expanding the view normally, but since the rewriter runs before the planner does inheritance expansion, it would take some very fundamental refactoring to make that possible. There are probably a lot of other parts of the system that don't cope well with such a situation, too. For now, just forbid it. Per bug #16856 from Yang Lin. Back-patch to all supported branches. (In versions before v10, this includes back-patching the portion of commit 501ed02cf that added has_superclass(). Perhaps the lack of that infrastructure partially explains the missing check.) Discussion: https://postgr.es/m/16856-0363e05c6e1612fd@postgresql.org
2021-02-06 21:17:01 +01:00
* has_superclass - does this relation inherit from another?
*
* Unlike has_subclass, this can be relied on to give an accurate answer.
* However, the caller must hold a lock on the given relation so that it
* can't be concurrently added to or removed from an inheritance hierarchy.
Fix transition tables for partition/inheritance. We disallow row-level triggers with transition tables on child tables. Transition tables for triggers on the parent table contain only those columns present in the parent. (We can't mix tuple formats in a single transition table.) Patch by Thomas Munro Discussion: https://postgr.es/m/CA%2BTgmoZzTBBAsEUh4MazAN7ga%3D8SsMC-Knp-6cetts9yNZUCcg%40mail.gmail.com
2017-06-28 19:55:03 +02:00
*/
bool
has_superclass(Oid relationId)
{
Relation catalog;
SysScanDesc scan;
ScanKeyData skey;
bool result;
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
catalog = table_open(InheritsRelationId, AccessShareLock);
Fix transition tables for partition/inheritance. We disallow row-level triggers with transition tables on child tables. Transition tables for triggers on the parent table contain only those columns present in the parent. (We can't mix tuple formats in a single transition table.) Patch by Thomas Munro Discussion: https://postgr.es/m/CA%2BTgmoZzTBBAsEUh4MazAN7ga%3D8SsMC-Knp-6cetts9yNZUCcg%40mail.gmail.com
2017-06-28 19:55:03 +02:00
ScanKeyInit(&skey, Anum_pg_inherits_inhrelid, BTEqualStrategyNumber,
F_OIDEQ, ObjectIdGetDatum(relationId));
scan = systable_beginscan(catalog, InheritsRelidSeqnoIndexId, true,
NULL, 1, &skey);
result = HeapTupleIsValid(systable_getnext(scan));
systable_endscan(scan);
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(catalog, AccessShareLock);
Fix transition tables for partition/inheritance. We disallow row-level triggers with transition tables on child tables. Transition tables for triggers on the parent table contain only those columns present in the parent. (We can't mix tuple formats in a single transition table.) Patch by Thomas Munro Discussion: https://postgr.es/m/CA%2BTgmoZzTBBAsEUh4MazAN7ga%3D8SsMC-Knp-6cetts9yNZUCcg%40mail.gmail.com
2017-06-28 19:55:03 +02:00
return result;
}
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
/*
* Given two type OIDs, determine whether the first is a complex type
* (class type) that inherits from the second.
Support domains over composite types. This is the last major omission in our domains feature: you can now make a domain over anything that's not a pseudotype. The major complication from an implementation standpoint is that places that might be creating tuples of a domain type now need to be prepared to apply domain_check(). It seems better that unprepared code fail with an error like "<type> is not composite" than that it silently fail to apply domain constraints. Therefore, relevant infrastructure like get_func_result_type() and lookup_rowtype_tupdesc() has been adjusted to treat domain-over-composite as a distinct case that unprepared code won't recognize, rather than just transparently treating it the same as plain composite. This isn't a 100% solution to the possibility of overlooked domain checks, but it catches most places. In passing, improve typcache.c's support for domains (it can now cache the identity of a domain's base type), and rewrite the argument handling logic in jsonfuncs.c's populate_record[set]_worker to reduce duplicative per-call lookups. I believe this is code-complete so far as the core and contrib code go. The PLs need varying amounts of work, which will be tackled in followup patches. Discussion: https://postgr.es/m/4206.1499798337@sss.pgh.pa.us
2017-10-26 19:47:45 +02:00
*
* This essentially asks whether the first type is guaranteed to be coercible
* to the second. Therefore, we allow the first type to be a domain over a
* complex type that inherits from the second; that creates no difficulties.
* But the second type cannot be a domain.
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
*/
bool
typeInheritsFrom(Oid subclassTypeId, Oid superclassTypeId)
{
bool result = false;
Oid subclassRelid;
Oid superclassRelid;
Relation inhrel;
List *visited,
*queue;
ListCell *queue_item;
/* We need to work with the associated relation OIDs */
Support domains over composite types. This is the last major omission in our domains feature: you can now make a domain over anything that's not a pseudotype. The major complication from an implementation standpoint is that places that might be creating tuples of a domain type now need to be prepared to apply domain_check(). It seems better that unprepared code fail with an error like "<type> is not composite" than that it silently fail to apply domain constraints. Therefore, relevant infrastructure like get_func_result_type() and lookup_rowtype_tupdesc() has been adjusted to treat domain-over-composite as a distinct case that unprepared code won't recognize, rather than just transparently treating it the same as plain composite. This isn't a 100% solution to the possibility of overlooked domain checks, but it catches most places. In passing, improve typcache.c's support for domains (it can now cache the identity of a domain's base type), and rewrite the argument handling logic in jsonfuncs.c's populate_record[set]_worker to reduce duplicative per-call lookups. I believe this is code-complete so far as the core and contrib code go. The PLs need varying amounts of work, which will be tackled in followup patches. Discussion: https://postgr.es/m/4206.1499798337@sss.pgh.pa.us
2017-10-26 19:47:45 +02:00
subclassRelid = typeOrDomainTypeRelid(subclassTypeId);
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
if (subclassRelid == InvalidOid)
Support domains over composite types. This is the last major omission in our domains feature: you can now make a domain over anything that's not a pseudotype. The major complication from an implementation standpoint is that places that might be creating tuples of a domain type now need to be prepared to apply domain_check(). It seems better that unprepared code fail with an error like "<type> is not composite" than that it silently fail to apply domain constraints. Therefore, relevant infrastructure like get_func_result_type() and lookup_rowtype_tupdesc() has been adjusted to treat domain-over-composite as a distinct case that unprepared code won't recognize, rather than just transparently treating it the same as plain composite. This isn't a 100% solution to the possibility of overlooked domain checks, but it catches most places. In passing, improve typcache.c's support for domains (it can now cache the identity of a domain's base type), and rewrite the argument handling logic in jsonfuncs.c's populate_record[set]_worker to reduce duplicative per-call lookups. I believe this is code-complete so far as the core and contrib code go. The PLs need varying amounts of work, which will be tackled in followup patches. Discussion: https://postgr.es/m/4206.1499798337@sss.pgh.pa.us
2017-10-26 19:47:45 +02:00
return false; /* not a complex type or domain over one */
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
superclassRelid = typeidTypeRelid(superclassTypeId);
if (superclassRelid == InvalidOid)
return false; /* not a complex type */
/* No point in searching if the superclass has no subclasses */
if (!has_subclass(superclassRelid))
return false;
/*
* Begin the search at the relation itself, so add its relid to the queue.
*/
queue = list_make1_oid(subclassRelid);
visited = NIL;
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
inhrel = table_open(InheritsRelationId, AccessShareLock);
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
/*
* Use queue to do a breadth-first traversal of the inheritance graph from
* the relid supplied up to the root. Notice that we append to the queue
* inside the loop --- this is okay because the foreach() macro doesn't
* advance queue_item until the next loop iteration begins.
*/
foreach(queue_item, queue)
{
Oid this_relid = lfirst_oid(queue_item);
ScanKeyData skey;
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
SysScanDesc inhscan;
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
HeapTuple inhtup;
/*
* If we've seen this relid already, skip it. This avoids extra work
* in multiple-inheritance scenarios, and also protects us from an
* infinite loop in case there is a cycle in pg_inherits (though
* theoretically that shouldn't happen).
*/
if (list_member_oid(visited, this_relid))
continue;
/*
* Okay, this is a not-yet-seen relid. Add it to the list of
* already-visited OIDs, then find all the types this relid inherits
* from and add them to the queue.
*/
visited = lappend_oid(visited, this_relid);
ScanKeyInit(&skey,
Anum_pg_inherits_inhrelid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(this_relid));
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
inhscan = systable_beginscan(inhrel, InheritsRelidSeqnoIndexId, true,
Use an MVCC snapshot, rather than SnapshotNow, for catalog scans. SnapshotNow scans have the undesirable property that, in the face of concurrent updates, the scan can fail to see either the old or the new versions of the row. In many cases, we work around this by requiring DDL operations to hold AccessExclusiveLock on the object being modified; in some cases, the existing locking is inadequate and random failures occur as a result. This commit doesn't change anything related to locking, but will hopefully pave the way to allowing lock strength reductions in the future. The major issue has held us back from making this change in the past is that taking an MVCC snapshot is significantly more expensive than using a static special snapshot such as SnapshotNow. However, testing of various worst-case scenarios reveals that this problem is not severe except under fairly extreme workloads. To mitigate those problems, we avoid retaking the MVCC snapshot for each new scan; instead, we take a new snapshot only when invalidation messages have been processed. The catcache machinery already requires that invalidation messages be sent before releasing the related heavyweight lock; else other backends might rely on locally-cached data rather than scanning the catalog at all. Thus, making snapshot reuse dependent on the same guarantees shouldn't break anything that wasn't already subtly broken. Patch by me. Review by Michael Paquier and Andres Freund.
2013-07-02 15:47:01 +02:00
NULL, 1, &skey);
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
while ((inhtup = systable_getnext(inhscan)) != NULL)
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
{
Form_pg_inherits inh = (Form_pg_inherits) GETSTRUCT(inhtup);
Oid inhparent = inh->inhparent;
/* If this is the target superclass, we're done */
if (inhparent == superclassRelid)
{
result = true;
break;
}
/* Else add to queue */
queue = lappend_oid(queue, inhparent);
}
Add an index on pg_inherits.inhparent, and use it to avoid seqscans in find_inheritance_children(). This is a complete no-op in databases without any inheritance. In databases where there are just a few entries in pg_inherits, it could conceivably be a small loss. However, in databases with many inheritance parents, it can be a big win.
2009-12-29 23:00:14 +01:00
systable_endscan(inhscan);
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
if (result)
break;
}
/* clean up ... */
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(inhrel, AccessShareLock);
Do some minor code refactoring in preparation for changing the APIs of find_inheritance_children() and find_all_inheritors(). I got annoyed that these are buried inside the planner but mostly used elsewhere. So, create a new file catalog/pg_inherits.c and put them there, along with a couple of other functions that search pg_inherits. The code that modifies pg_inherits is (still) in tablecmds.c --- it's kind of entangled with unrelated code that modifies pg_depend and other stuff, so pulling it out seemed like a bigger change than I wanted to make right now. But this file provides a natural home for it if anyone ever gets around to that. This commit just moves code around; it doesn't change anything, except I succumbed to the temptation to make a couple of trivial optimizations in typeInheritsFrom().
2009-05-12 02:56:05 +02:00
list_free(visited);
list_free(queue);
return result;
}
Local partitioned indexes When CREATE INDEX is run on a partitioned table, create catalog entries for an index on the partitioned table (which is just a placeholder since the table proper has no data of its own), and recurse to create actual indexes on the existing partitions; create them in future partitions also. As a convenience gadget, if the new index definition matches some existing index in partitions, these are picked up and used instead of creating new ones. Whichever way these indexes come about, they become attached to the index on the parent table and are dropped alongside it, and cannot be dropped on isolation unless they are detached first. To support pg_dump'ing these indexes, add commands CREATE INDEX ON ONLY <table> (which creates the index on the parent partitioned table, without recursing) and ALTER INDEX ATTACH PARTITION (which is used after the indexes have been created individually on each partition, to attach them to the parent index). These reconstruct prior database state exactly. Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit Langote, Jesper Pedersen, Simon Riggs, David Rowley Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
2018-01-19 15:49:22 +01:00
/*
* Create a single pg_inherits row with the given data
*/
void
StoreSingleInheritance(Oid relationId, Oid parentOid, int32 seqNumber)
{
Datum values[Natts_pg_inherits];
bool nulls[Natts_pg_inherits];
HeapTuple tuple;
Relation inhRelation;
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
inhRelation = table_open(InheritsRelationId, RowExclusiveLock);
Local partitioned indexes When CREATE INDEX is run on a partitioned table, create catalog entries for an index on the partitioned table (which is just a placeholder since the table proper has no data of its own), and recurse to create actual indexes on the existing partitions; create them in future partitions also. As a convenience gadget, if the new index definition matches some existing index in partitions, these are picked up and used instead of creating new ones. Whichever way these indexes come about, they become attached to the index on the parent table and are dropped alongside it, and cannot be dropped on isolation unless they are detached first. To support pg_dump'ing these indexes, add commands CREATE INDEX ON ONLY <table> (which creates the index on the parent partitioned table, without recursing) and ALTER INDEX ATTACH PARTITION (which is used after the indexes have been created individually on each partition, to attach them to the parent index). These reconstruct prior database state exactly. Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit Langote, Jesper Pedersen, Simon Riggs, David Rowley Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
2018-01-19 15:49:22 +01:00
/*
* Make the pg_inherits entry
*/
values[Anum_pg_inherits_inhrelid - 1] = ObjectIdGetDatum(relationId);
values[Anum_pg_inherits_inhparent - 1] = ObjectIdGetDatum(parentOid);
values[Anum_pg_inherits_inhseqno - 1] = Int32GetDatum(seqNumber);
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 22:00:28 +01:00
values[Anum_pg_inherits_inhdetachpending - 1] = BoolGetDatum(false);
Local partitioned indexes When CREATE INDEX is run on a partitioned table, create catalog entries for an index on the partitioned table (which is just a placeholder since the table proper has no data of its own), and recurse to create actual indexes on the existing partitions; create them in future partitions also. As a convenience gadget, if the new index definition matches some existing index in partitions, these are picked up and used instead of creating new ones. Whichever way these indexes come about, they become attached to the index on the parent table and are dropped alongside it, and cannot be dropped on isolation unless they are detached first. To support pg_dump'ing these indexes, add commands CREATE INDEX ON ONLY <table> (which creates the index on the parent partitioned table, without recursing) and ALTER INDEX ATTACH PARTITION (which is used after the indexes have been created individually on each partition, to attach them to the parent index). These reconstruct prior database state exactly. Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit Langote, Jesper Pedersen, Simon Riggs, David Rowley Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
2018-01-19 15:49:22 +01:00
memset(nulls, 0, sizeof(nulls));
tuple = heap_form_tuple(RelationGetDescr(inhRelation), values, nulls);
CatalogTupleInsert(inhRelation, tuple);
heap_freetuple(tuple);
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(inhRelation, RowExclusiveLock);
Local partitioned indexes When CREATE INDEX is run on a partitioned table, create catalog entries for an index on the partitioned table (which is just a placeholder since the table proper has no data of its own), and recurse to create actual indexes on the existing partitions; create them in future partitions also. As a convenience gadget, if the new index definition matches some existing index in partitions, these are picked up and used instead of creating new ones. Whichever way these indexes come about, they become attached to the index on the parent table and are dropped alongside it, and cannot be dropped on isolation unless they are detached first. To support pg_dump'ing these indexes, add commands CREATE INDEX ON ONLY <table> (which creates the index on the parent partitioned table, without recursing) and ALTER INDEX ATTACH PARTITION (which is used after the indexes have been created individually on each partition, to attach them to the parent index). These reconstruct prior database state exactly. Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit Langote, Jesper Pedersen, Simon Riggs, David Rowley Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
2018-01-19 15:49:22 +01:00
}
/*
* DeleteInheritsTuple
*
* Delete pg_inherits tuples with the given inhrelid. inhparent may be given
* as InvalidOid, in which case all tuples matching inhrelid are deleted;
* otherwise only delete tuples with the specified inhparent.
*
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 22:00:28 +01:00
* expect_detach_pending is the expected state of the inhdetachpending flag.
* If the catalog row does not match that state, an error is raised.
*
* childname is the partition name, if a table; pass NULL for regular
* inheritance or when working with other relation kinds.
*
Local partitioned indexes When CREATE INDEX is run on a partitioned table, create catalog entries for an index on the partitioned table (which is just a placeholder since the table proper has no data of its own), and recurse to create actual indexes on the existing partitions; create them in future partitions also. As a convenience gadget, if the new index definition matches some existing index in partitions, these are picked up and used instead of creating new ones. Whichever way these indexes come about, they become attached to the index on the parent table and are dropped alongside it, and cannot be dropped on isolation unless they are detached first. To support pg_dump'ing these indexes, add commands CREATE INDEX ON ONLY <table> (which creates the index on the parent partitioned table, without recursing) and ALTER INDEX ATTACH PARTITION (which is used after the indexes have been created individually on each partition, to attach them to the parent index). These reconstruct prior database state exactly. Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit Langote, Jesper Pedersen, Simon Riggs, David Rowley Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
2018-01-19 15:49:22 +01:00
* Returns whether at least one row was deleted.
*/
bool
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 22:00:28 +01:00
DeleteInheritsTuple(Oid inhrelid, Oid inhparent, bool expect_detach_pending,
const char *childname)
Local partitioned indexes When CREATE INDEX is run on a partitioned table, create catalog entries for an index on the partitioned table (which is just a placeholder since the table proper has no data of its own), and recurse to create actual indexes on the existing partitions; create them in future partitions also. As a convenience gadget, if the new index definition matches some existing index in partitions, these are picked up and used instead of creating new ones. Whichever way these indexes come about, they become attached to the index on the parent table and are dropped alongside it, and cannot be dropped on isolation unless they are detached first. To support pg_dump'ing these indexes, add commands CREATE INDEX ON ONLY <table> (which creates the index on the parent partitioned table, without recursing) and ALTER INDEX ATTACH PARTITION (which is used after the indexes have been created individually on each partition, to attach them to the parent index). These reconstruct prior database state exactly. Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit Langote, Jesper Pedersen, Simon Riggs, David Rowley Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
2018-01-19 15:49:22 +01:00
{
bool found = false;
Relation catalogRelation;
ScanKeyData key;
SysScanDesc scan;
HeapTuple inheritsTuple;
/*
* Find pg_inherits entries by inhrelid.
*/
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
catalogRelation = table_open(InheritsRelationId, RowExclusiveLock);
Local partitioned indexes When CREATE INDEX is run on a partitioned table, create catalog entries for an index on the partitioned table (which is just a placeholder since the table proper has no data of its own), and recurse to create actual indexes on the existing partitions; create them in future partitions also. As a convenience gadget, if the new index definition matches some existing index in partitions, these are picked up and used instead of creating new ones. Whichever way these indexes come about, they become attached to the index on the parent table and are dropped alongside it, and cannot be dropped on isolation unless they are detached first. To support pg_dump'ing these indexes, add commands CREATE INDEX ON ONLY <table> (which creates the index on the parent partitioned table, without recursing) and ALTER INDEX ATTACH PARTITION (which is used after the indexes have been created individually on each partition, to attach them to the parent index). These reconstruct prior database state exactly. Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit Langote, Jesper Pedersen, Simon Riggs, David Rowley Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
2018-01-19 15:49:22 +01:00
ScanKeyInit(&key,
Anum_pg_inherits_inhrelid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(inhrelid));
scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId,
true, NULL, 1, &key);
while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
{
Oid parent;
/* Compare inhparent if it was given, and do the actual deletion. */
parent = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhparent;
if (!OidIsValid(inhparent) || parent == inhparent)
{
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 22:00:28 +01:00
bool detach_pending;
detach_pending =
((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhdetachpending;
/*
* Raise error depending on state. This should only happen for
* partitions, but we have no way to cross-check.
*/
if (detach_pending && !expect_detach_pending)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("cannot detach partition \"%s\"",
childname ? childname : "unknown relation"),
errdetail("The partition is being detached concurrently or has an unfinished detach."),
Message style improvements
2021-06-28 08:36:44 +02:00
errhint("Use ALTER TABLE ... DETACH PARTITION ... FINALIZE to complete the pending detach operation.")));
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 22:00:28 +01:00
if (!detach_pending && expect_detach_pending)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("cannot complete detaching partition \"%s\"",
childname ? childname : "unknown relation"),
errdetail("There's no pending concurrent detach.")));
Local partitioned indexes When CREATE INDEX is run on a partitioned table, create catalog entries for an index on the partitioned table (which is just a placeholder since the table proper has no data of its own), and recurse to create actual indexes on the existing partitions; create them in future partitions also. As a convenience gadget, if the new index definition matches some existing index in partitions, these are picked up and used instead of creating new ones. Whichever way these indexes come about, they become attached to the index on the parent table and are dropped alongside it, and cannot be dropped on isolation unless they are detached first. To support pg_dump'ing these indexes, add commands CREATE INDEX ON ONLY <table> (which creates the index on the parent partitioned table, without recursing) and ALTER INDEX ATTACH PARTITION (which is used after the indexes have been created individually on each partition, to attach them to the parent index). These reconstruct prior database state exactly. Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit Langote, Jesper Pedersen, Simon Riggs, David Rowley Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
2018-01-19 15:49:22 +01:00
CatalogTupleDelete(catalogRelation, &inheritsTuple->t_self);
found = true;
}
}
/* Done */
systable_endscan(scan);
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(catalogRelation, RowExclusiveLock);
Local partitioned indexes When CREATE INDEX is run on a partitioned table, create catalog entries for an index on the partitioned table (which is just a placeholder since the table proper has no data of its own), and recurse to create actual indexes on the existing partitions; create them in future partitions also. As a convenience gadget, if the new index definition matches some existing index in partitions, these are picked up and used instead of creating new ones. Whichever way these indexes come about, they become attached to the index on the parent table and are dropped alongside it, and cannot be dropped on isolation unless they are detached first. To support pg_dump'ing these indexes, add commands CREATE INDEX ON ONLY <table> (which creates the index on the parent partitioned table, without recursing) and ALTER INDEX ATTACH PARTITION (which is used after the indexes have been created individually on each partition, to attach them to the parent index). These reconstruct prior database state exactly. Reviewed-by: (in alphabetical order) Peter Eisentraut, Robert Haas, Amit Langote, Jesper Pedersen, Simon Riggs, David Rowley Discussion: https://postgr.es/m/20171113170646.gzweigyrgg6pwsg4@alvherre.pgsql
2018-01-19 15:49:22 +01:00
return found;
}
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 22:00:28 +01:00
/*
* Return whether the pg_inherits tuple for a partition has the "detach
* pending" flag set.
*/
bool
PartitionHasPendingDetach(Oid partoid)
{
Relation catalogRelation;
ScanKeyData key;
SysScanDesc scan;
HeapTuple inheritsTuple;
/* We don't have a good way to verify it is in fact a partition */
/*
* Find the pg_inherits entry by inhrelid. (There should only be one.)
*/
catalogRelation = table_open(InheritsRelationId, RowExclusiveLock);
ScanKeyInit(&key,
Anum_pg_inherits_inhrelid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(partoid));
scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId,
true, NULL, 1, &key);
while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
{
bool detached;
detached =
((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhdetachpending;
/* Done */
systable_endscan(scan);
table_close(catalogRelation, RowExclusiveLock);
return detached;
}
elog(ERROR, "relation %u is not a partition", partoid);
return false; /* keep compiler quiet */
}