From fa6131377054d04f7c938b196b39eeb22784951b Mon Sep 17 00:00:00 2001 From: Noah Misch Date: Sat, 28 Dec 2024 07:16:22 -0800 Subject: In REASSIGN OWNED of a database, lock the tuple as mandated. Commit aac2c9b4fde889d13f859c233c2523345e72d32b mandated such locking and attempted to fulfill that mandate, but it missed REASSIGN OWNED. Hence, it remained possible to lose VACUUM's inplace update of datfrozenxid if a REASSIGN OWNED processed that database at the same time. This didn't affect the other inplace-updated catalog, pg_class. For pg_class, REASSIGN OWNED calls ATExecChangeOwner() instead of the generic AlterObjectOwner_internal(), and ATExecChangeOwner() fulfills the locking mandate. Like in GRANT, implement this by following the locking protocol for any catalog subject to the generic AlterObjectOwner_internal(). It would suffice to do this for IsInplaceUpdateOid() catalogs only. Back-patch to v13 (all supported versions). Kirill Reshke. Reported by Alexander Kukushkin. Discussion: https://postgr.es/m/CAFh8B=mpKjAy4Cuun-HP-f_vRzh2HSvYFG3rhVfYbfEBUhBAGg@mail.gmail.com --- src/backend/commands/alter.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'src/backend/commands/alter.c') diff --git a/src/backend/commands/alter.c b/src/backend/commands/alter.c index 4f99ebb4470..132283b1ef2 100644 --- a/src/backend/commands/alter.c +++ b/src/backend/commands/alter.c @@ -59,6 +59,7 @@ #include "miscadmin.h" #include "replication/logicalworker.h" #include "rewrite/rewriteDefine.h" +#include "storage/lmgr.h" #include "utils/acl.h" #include "utils/builtins.h" #include "utils/lsyscache.h" @@ -931,7 +932,9 @@ AlterObjectOwner_internal(Oid classId, Oid objectId, Oid new_ownerId) rel = table_open(catalogId, RowExclusiveLock); - oldtup = get_catalog_object_by_oid(rel, Anum_oid, objectId); + /* Search tuple and lock it. */ + oldtup = + get_catalog_object_by_oid_extended(rel, Anum_oid, objectId, true); if (oldtup == NULL) elog(ERROR, "cache lookup failed for object %u of catalog \"%s\"", objectId, RelationGetRelationName(rel)); @@ -1031,6 +1034,8 @@ AlterObjectOwner_internal(Oid classId, Oid objectId, Oid new_ownerId) /* Perform actual update */ CatalogTupleUpdate(rel, &newtup->t_self, newtup); + UnlockTuple(rel, &oldtup->t_self, InplaceUpdateTupleLock); + /* Update owner dependency reference */ changeDependencyOnOwner(classId, objectId, new_ownerId); @@ -1039,6 +1044,8 @@ AlterObjectOwner_internal(Oid classId, Oid objectId, Oid new_ownerId) pfree(nulls); pfree(replaces); } + else + UnlockTuple(rel, &oldtup->t_self, InplaceUpdateTupleLock); /* Note the post-alter hook gets classId not catalogId */ InvokeObjectPostAlterHook(classId, objectId, 0); -- cgit v1.2.3