From: Tom Lane Date: Tue, 31 Mar 2020 21:06:22 +0000 (-0400) Subject: Fix race condition in statext_store(). X-Git-Tag: REL_13_BETA1~400 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=fe3036527a1ff715bceb22ff5cba919001262a71;p=thirdparty%2Fpostgresql.git 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 --- diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c index 318fdb8f6dc..d1f818d49a8 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,