mirror of
https://github.com/postgres/postgres.git
synced 2025-08-19 23:22:23 +03:00
For inplace update durability, make heap_update() callers wait.
The previous commit fixed some ways of losing an inplace update. It
remained possible to lose one when a backend working toward a
heap_update() copied a tuple into memory just before inplace update of
that tuple. In catalogs eligible for inplace update, use LOCKTAG_TUPLE
to govern admission to the steps of copying an old tuple, modifying it,
and issuing heap_update(). This includes MERGE commands. To avoid
changing most of the pg_class DDL, don't require LOCKTAG_TUPLE when
holding a relation lock sufficient to exclude inplace updaters.
Back-patch to v12 (all supported versions). In v13 and v12, "UPDATE
pg_class" or "UPDATE pg_database" can still lose an inplace update. The
v14+ UPDATE fix needs commit 86dc90056d
,
and it wasn't worth reimplementing that fix without such infrastructure.
Reviewed by Nitin Motiani and (in earlier versions) Heikki Linnakangas.
Discussion: https://postgr.es/m/20231027214946.79.nmisch@google.com
This commit is contained in:
@@ -19,6 +19,7 @@
|
||||
#include "access/tableam.h"
|
||||
#include "access/transam.h"
|
||||
#include "access/xact.h"
|
||||
#include "catalog/catalog.h"
|
||||
#include "commands/trigger.h"
|
||||
#include "executor/executor.h"
|
||||
#include "executor/nodeModifyTable.h"
|
||||
@@ -481,8 +482,12 @@ ExecSimpleRelationUpdate(EState *estate, EPQState *epqstate,
|
||||
Relation rel = resultRelInfo->ri_RelationDesc;
|
||||
ItemPointer tid = &(searchslot->tts_tid);
|
||||
|
||||
/* For now we support only tables. */
|
||||
/*
|
||||
* We support only non-system tables, with
|
||||
* check_publication_add_relation() accountable.
|
||||
*/
|
||||
Assert(rel->rd_rel->relkind == RELKIND_RELATION);
|
||||
Assert(!IsCatalogRelation(rel));
|
||||
|
||||
CheckCmdReplicaIdentity(rel, CMD_UPDATE);
|
||||
|
||||
|
@@ -1282,6 +1282,7 @@ ExecUpdate(ModifyTableState *mtstate,
|
||||
}
|
||||
else
|
||||
{
|
||||
ItemPointerData lockedtid PG_USED_FOR_ASSERTS_ONLY;
|
||||
LockTupleMode lockmode;
|
||||
bool partition_constraint_failed;
|
||||
bool update_indexes;
|
||||
@@ -1472,6 +1473,26 @@ lreplace:
|
||||
if (resultRelationDesc->rd_att->constr)
|
||||
ExecConstraints(resultRelInfo, slot, estate);
|
||||
|
||||
/*
|
||||
* We lack the infrastructure to follow rules in README.tuplock
|
||||
* section "Locking to write inplace-updated tables". Specifically,
|
||||
* we lack infrastructure to lock tupleid before this file's
|
||||
* ExecProcNode() call fetches the tuple's old columns. Just take a
|
||||
* lock that silences check_lock_if_inplace_updateable_rel(). This
|
||||
* doesn't actually protect inplace updates like those rules intend,
|
||||
* so we may lose an inplace update that overlaps a superuser running
|
||||
* "UPDATE pg_class" or "UPDATE pg_database".
|
||||
*/
|
||||
#ifdef USE_ASSERT_CHECKING
|
||||
if (IsInplaceUpdateRelation(resultRelationDesc))
|
||||
{
|
||||
lockedtid = *tupleid;
|
||||
LockTuple(resultRelationDesc, &lockedtid, InplaceUpdateTupleLock);
|
||||
}
|
||||
else
|
||||
ItemPointerSetInvalid(&lockedtid);
|
||||
#endif
|
||||
|
||||
/*
|
||||
* replace the heap tuple
|
||||
*
|
||||
@@ -1488,6 +1509,11 @@ lreplace:
|
||||
true /* wait for commit */ ,
|
||||
&tmfd, &lockmode, &update_indexes);
|
||||
|
||||
#ifdef USE_ASSERT_CHECKING
|
||||
if (ItemPointerIsValid(&lockedtid))
|
||||
UnlockTuple(resultRelationDesc, &lockedtid, InplaceUpdateTupleLock);
|
||||
#endif
|
||||
|
||||
switch (result)
|
||||
{
|
||||
case TM_SelfModified:
|
||||
|
Reference in New Issue
Block a user