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 08e9bfcbf1857a94158c34dfd1bec1b806bd167c..ec974d11833a34d03072acc20923f0b143196fc8 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -13865,7 +13865,7 @@ ATExecDetachPartition(Relation rel, RangeVar *name)
                new_repl[Natts_pg_class];
    ObjectAddress address;
 
-   partRel = heap_openrv(name, AccessShareLock);
+   partRel = heap_openrv(name, ShareUpdateExclusiveLock);
 
    /* All inheritance related checks are performed within the function */
    RemoveInheritance(partRel, rel);