Fix lock level used for partition when detaching it

alvherre · alvherre · commit 7b14bcc06cc5 · 2018-12-20T16:42:13.000-03:00
For probably bogus reasons, we acquire only AccessShareLock on the partition when we try to detach it from its parent partitioned table. This can cause ugly things to happen if another transaction is doing any sort of DDL to the partition concurrently. Upgrade that lock to ShareUpdateExclusiveLock, which per discussion seems to be the minimum needed. Reported by Robert Haas. Discussion: https://postgr.es/m/CA+TgmoYruJQ+2qnFLtF1xQtr71pdwgfxy3Ziy-TxV28M6pEmyA@mail.gmail.com
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
@@ -14588,7 +14588,7 @@ ATExecDetachPartition(Relation rel, RangeVar *name)
 	if (OidIsValid(defaultPartOid))
 		LockRelationOid(defaultPartOid, AccessExclusiveLock);
 
-	partRel = heap_openrv(name, AccessShareLock);
+	partRel = heap_openrv(name, ShareUpdateExclusiveLock);
 
 	/* All inheritance related checks are performed within the function */
 	RemoveInheritance(partRel, rel);
