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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 8590c942c1
commit 5c837f8fa0
19 changed files with 490 additions and 49 deletions
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5
src/include/utils/syscache.h
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@@ -139,9 +139,14 @@ extern HeapTuple SearchSysCache4(int cacheId,
extern void ReleaseSysCache(HeapTuple tuple);
extern HeapTuple SearchSysCacheLocked1(int cacheId,
Datum key1);
/* convenience routines */
extern HeapTuple SearchSysCacheCopy(int cacheId,
Datum key1, Datum key2, Datum key3, Datum key4);
extern HeapTuple SearchSysCacheLockedCopy1(int cacheId,
Datum key1);
extern bool SearchSysCacheExists(int cacheId,
Datum key1, Datum key2, Datum key3, Datum key4);
extern Oid GetSysCacheOid(int cacheId, AttrNumber oidcol,