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For inplace update durability, make heap_update() callers wait.

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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:
Noah Misch
2024-09-24 15:25:18 -07:00
parent a07e03fd8f
commit aac2c9b4fd
20 changed files with 498 additions and 57 deletions
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28
src/backend/commands/tablecmds.c
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@ -3593,6 +3593,7 @@ SetRelationTableSpace(Relation rel,
{
Relation pg_class;
HeapTuple tuple;
ItemPointerData otid;
Form_pg_class rd_rel;
Oid reloid = RelationGetRelid(rel);
@ -3601,9 +3602,10 @@ SetRelationTableSpace(Relation rel,
/* Get a modifiable copy of the relation's pg_class row. */
pg_class = table_open(RelationRelationId, RowExclusiveLock);
tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(reloid));
tuple = SearchSysCacheLockedCopy1(RELOID, ObjectIdGetDatum(reloid));
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for relation %u", reloid);
otid = tuple->t_self;
rd_rel = (Form_pg_class) GETSTRUCT(tuple);
/* Update the pg_class row. */
@ -3611,7 +3613,8 @@ SetRelationTableSpace(Relation rel,
InvalidOid : newTableSpaceId;
if (RelFileNumberIsValid(newRelFilenumber))
rd_rel->relfilenode = newRelFilenumber;
CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
CatalogTupleUpdate(pg_class, &otid, tuple);
UnlockTuple(pg_class, &otid, InplaceUpdateTupleLock);
/*
* Record dependency on tablespace. This is only required for relations
@ -4105,6 +4108,7 @@ RenameRelationInternal(Oid myrelid, const char *newrelname, bool is_internal, bo
{
Relation targetrelation;
Relation relrelation; /* for RELATION relation */
ItemPointerData otid;
HeapTuple reltup;
Form_pg_class relform;
Oid namespaceId;
@ -4127,7 +4131,8 @@ RenameRelationInternal(Oid myrelid, const char *newrelname, bool is_internal, bo
*/
relrelation = table_open(RelationRelationId, RowExclusiveLock);
reltup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(myrelid));
reltup = SearchSysCacheLockedCopy1(RELOID, ObjectIdGetDatum(myrelid));
otid = reltup->t_self;
if (!HeapTupleIsValid(reltup)) /* shouldn't happen */
elog(ERROR, "cache lookup failed for relation %u", myrelid);
relform = (Form_pg_class) GETSTRUCT(reltup);
@ -4154,7 +4159,8 @@ RenameRelationInternal(Oid myrelid, const char *newrelname, bool is_internal, bo
*/
namestrcpy(&(relform->relname), newrelname);
CatalogTupleUpdate(relrelation, &reltup->t_self, reltup);
CatalogTupleUpdate(relrelation, &otid, reltup);
UnlockTuple(relrelation, &otid, InplaceUpdateTupleLock);
InvokeObjectPostAlterHookArg(RelationRelationId, myrelid, 0,
InvalidOid, is_internal);
@ -15072,7 +15078,7 @@ ATExecSetRelOptions(Relation rel, List *defList, AlterTableType operation,
/* Fetch heap tuple */
relid = RelationGetRelid(rel);
tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
tuple = SearchSysCacheLocked1(RELOID, ObjectIdGetDatum(relid));
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for relation %u", relid);
@ -15176,6 +15182,7 @@ ATExecSetRelOptions(Relation rel, List *defList, AlterTableType operation,
repl_val, repl_null, repl_repl);
CatalogTupleUpdate(pgclass, &newtuple->t_self, newtuple);
UnlockTuple(pgclass, &tuple->t_self, InplaceUpdateTupleLock);
InvokeObjectPostAlterHook(RelationRelationId, RelationGetRelid(rel), 0);
@ -17329,7 +17336,8 @@ AlterRelationNamespaceInternal(Relation classRel, Oid relOid,
ObjectAddress thisobj;
bool already_done = false;
classTup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relOid));
/* no rel lock for relkind=c so use LOCKTAG_TUPLE */
classTup = SearchSysCacheLockedCopy1(RELOID, ObjectIdGetDatum(relOid));
if (!HeapTupleIsValid(classTup))
elog(ERROR, "cache lookup failed for relation %u", relOid);
classForm = (Form_pg_class) GETSTRUCT(classTup);
@ -17348,6 +17356,8 @@ AlterRelationNamespaceInternal(Relation classRel, Oid relOid,
already_done = object_address_present(&thisobj, objsMoved);
if (!already_done && oldNspOid != newNspOid)
{
ItemPointerData otid = classTup->t_self;
/* check for duplicate name (more friendly than unique-index failure) */
if (get_relname_relid(NameStr(classForm->relname),
newNspOid) != InvalidOid)
@ -17360,7 +17370,9 @@ AlterRelationNamespaceInternal(Relation classRel, Oid relOid,
/* classTup is a copy, so OK to scribble on */
classForm->relnamespace = newNspOid;
CatalogTupleUpdate(classRel, &classTup->t_self, classTup);
CatalogTupleUpdate(classRel, &otid, classTup);
UnlockTuple(classRel, &otid, InplaceUpdateTupleLock);
/* Update dependency on schema if caller said so */
if (hasDependEntry &&
@ -17372,6 +17384,8 @@ AlterRelationNamespaceInternal(Relation classRel, Oid relOid,
elog(ERROR, "could not change schema dependency for relation \"%s\"",
NameStr(classForm->relname));
}
else
UnlockTuple(classRel, &classTup->t_self, InplaceUpdateTupleLock);
if (!already_done)
{
add_exact_object_address(&thisobj, objsMoved);