Fix lock level used for partition when detaching it

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
index ce0c7b3153fbaf22d1ff2ce5815f3cd5271fe28a..588c1ec5365281d39faf7817c8add6072bb28d8d 100644 (file)
--- 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);