From 5c837f8fa022ff9d9ebced71fdcae273fe433570 Mon Sep 17 00:00:00 2001 From: Noah Misch Date: Tue, 24 Sep 2024 15:25:18 -0700 Subject: 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 86dc90056dfdbd9d1b891718d2e5614e3e432f35, 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 --- src/backend/executor/execMain.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'src/backend/executor/execMain.c') diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c index b24a05f156a..2c7e35196ad 100644 --- a/src/backend/executor/execMain.c +++ b/src/backend/executor/execMain.c @@ -43,6 +43,7 @@ #include "access/tableam.h" #include "access/transam.h" #include "access/xact.h" +#include "catalog/catalog.h" #include "catalog/namespace.h" #include "catalog/partition.h" #include "catalog/pg_publication.h" @@ -999,6 +1000,10 @@ CheckValidResultRel(ResultRelInfo *resultRelInfo, CmdType operation) TriggerDesc *trigDesc = resultRel->trigdesc; FdwRoutine *fdwroutine; + /* Expect a fully-formed ResultRelInfo from InitResultRelInfo(). */ + Assert(resultRelInfo->ri_needLockTagTuple == + IsInplaceUpdateRelation(resultRel)); + switch (resultRel->rd_rel->relkind) { case RELKIND_RELATION: @@ -1207,6 +1212,8 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo, resultRelInfo->ri_NumIndices = 0; resultRelInfo->ri_IndexRelationDescs = NULL; resultRelInfo->ri_IndexRelationInfo = NULL; + resultRelInfo->ri_needLockTagTuple = + IsInplaceUpdateRelation(resultRelationDesc); /* make a copy so as not to depend on relcache info not changing... */ resultRelInfo->ri_TrigDesc = CopyTriggerDesc(resultRelationDesc->trigdesc); if (resultRelInfo->ri_TrigDesc) -- cgit v1.2.3