On 2021-Feb-26, Alvaro Herrera wrote:
> Hmm, but if we take this approach, then we're still vulnerable to the
> problem that somebody can do DETACH CONCURRENTLY and cancel the wait (or
> crash the server), then mess up the state before doing DETACH FINALIZE:
> when they cancel the wait, the lock will be released.
>
> I think the right fix is to disallow any action on a partition which is
> pending detach other than DETACH FINALIZE. (Didn't do that here.)
Here's a fixup patch to do it that way. I tried running the commands
you showed and one of them immediately dies with the new error message;
I can't cause the bogus constraint to show up anymore.
I'll clean this up for a real submission tomorrow.
--
Álvaro Herrera 39°49'30"S 73°17'W
"The Gord often wonders why people threaten never to come back after they've
been told never to return" (www.actsofgord.com)
diff --git a/src/backend/catalog/pg_inherits.c
b/src/backend/catalog/pg_inherits.c
index 3fd0880ca0..83093f9730 100644
--- a/src/backend/catalog/pg_inherits.c
+++ b/src/backend/catalog/pg_inherits.c
@@ -535,3 +535,39 @@ DeleteInheritsTuple(Oid inhrelid, Oid inhparent, bool
detached,
return found;
}
+
+bool
+PartitionHasPendingDetach(Oid partoid)
+{
+ Relation catalogRelation;
+ ScanKeyData key;
+ SysScanDesc scan;
+ HeapTuple inheritsTuple;
+
+ /*
+ * Find pg_inherits entries by inhrelid.
+ */
+ catalogRelation = table_open(InheritsRelationId, RowExclusiveLock);
+ ScanKeyInit(&key,
+ Anum_pg_inherits_inhrelid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(partoid));
+ scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId,
+ true, NULL, 1, &key);
+
+ while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
+ {
+ bool detached;
+
+ detached = ((Form_pg_inherits)
GETSTRUCT(inheritsTuple))->inhdetached;
+
+ /* Done */
+ systable_endscan(scan);
+ table_close(catalogRelation, RowExclusiveLock);
+
+ return detached;
+ }
+
+ elog(ERROR, "relation %u is not a partition", partoid);
+ return false; /* keep compiler quiet */
+}
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 5986b4dd56..5074c0ff2b 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -17106,6 +17106,8 @@ ATExecDetachPartition(List **wqueue, AlteredTableInfo
*tab, Relation rel,
*/
partRel = table_openrv(name, concurrent ? ShareLock :
AccessExclusiveLock);
+ if (PartitionHasPendingDetach(RelationGetRelid(partRel)))
+ elog(ERROR, "hey, don't!");
/*
* Check inheritance conditions and either delete the pg_inherits row
diff --git a/src/include/catalog/pg_inherits.h
b/src/include/catalog/pg_inherits.h
index 155596907c..19243ea9e4 100644
--- a/src/include/catalog/pg_inherits.h
+++ b/src/include/catalog/pg_inherits.h
@@ -61,5 +61,6 @@ extern void StoreSingleInheritance(Oid relationId, Oid
parentOid,
int32
seqNumber);
extern bool DeleteInheritsTuple(Oid inhrelid, Oid inhparent, bool
allow_detached,
const char
*childname);
+extern bool PartitionHasPendingDetach(Oid partoid);
#endif /* PG_INHERITS_H */
