postgres.git / summary / log / commit / refs
commit 6c426cd43790d56e6b96c21ae2d968ceb733bdde
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue Mar 31 21:06:22 2020 +0000
First released in: 13.0, 12.3
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 4516c97f406..d8e51500232 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -322,12 +322,14 @@ 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));
@@ -371,8 +373,6 @@ 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,
[parent: 1fd0eee66f1e]