From fe3036527a1ff715bceb22ff5cba919001262a71 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 31 Mar 2020 17:06:22 -0400 Subject: [PATCH] Fix race condition in statext_store(). Must hold some lock on the pg_statistic_ext_data catalog *before* we look up the tuple we aim to replace. Otherwise a concurrent VACUUM FULL or similar operation could move it to a different TID, leaving us trying to replace the wrong tuple. Back-patch to v12 where this got broken. Credit goes to Dean Rasheed; I'm just doing the clerical work. Discussion: https://postgr.es/m/CAEZATCU0zHMDiQV0g8P2U+YSP9C1idUPrn79DajsbonwkN0xvQ@mail.gmail.com --- src/backend/statistics/extended_stats.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c index 318fdb8f6d..d1f818d49a 100644 --- a/src/backend/statistics/extended_stats.c +++ b/src/backend/statistics/extended_stats.c @@ -493,12 +493,14 @@ statext_store(Oid statOid, MVNDistinct *ndistinct, MVDependencies *dependencies, MCVList *mcv, VacAttrStats **stats) { + Relation pg_stextdata; HeapTuple stup, oldtup; Datum values[Natts_pg_statistic_ext_data]; bool nulls[Natts_pg_statistic_ext_data]; bool replaces[Natts_pg_statistic_ext_data]; - Relation pg_stextdata; + + pg_stextdata = table_open(StatisticExtDataRelationId, RowExclusiveLock); memset(nulls, true, sizeof(nulls)); memset(replaces, false, sizeof(replaces)); @@ -542,8 +544,6 @@ statext_store(Oid statOid, elog(ERROR, "cache lookup failed for statistics object %u", statOid); /* replace it */ - pg_stextdata = table_open(StatisticExtDataRelationId, RowExclusiveLock); - stup = heap_modify_tuple(oldtup, RelationGetDescr(pg_stextdata), values,