index 3c42e160b2dbe57f454b798c6bef99f798974fbe..7859ef13ac4aafaf600a1923ddf3aa94b69f967b 100644 (file)
@@ -13489,9 +13489,20 @@ ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd)
/*
* Prevent circularity by seeing if rel is a partition of attachrel. (In
* particular, this disallows making a rel a partition of itself.)
+ *
+ * We do that by checking if rel is a member of the list of attachRel's
+ * partitions provided the latter is partitioned at all. We want to avoid
+ * having to construct this list again, so we request the strongest lock
+ * on all partitions. We need the strongest lock, because we may decide
+ * to scan them if we find out that the table being attached (or its leaf
+ * partitions) may contain rows that violate the partition constraint.
+ * If the table has a constraint that would prevent such rows, which by
+ * definition is present in all the partitions, we need not scan the
+ * table, nor its partitions. But we cannot risk a deadlock by taking a
+ * weaker lock now and the stronger one only when needed.
*/
attachrel_children = find_all_inheritors(RelationGetRelid(attachrel),
- AccessShareLock, NULL);
+ AccessExclusiveLock, NULL);
if (list_member_oid(attachrel_children, RelationGetRelid(rel)))
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_TABLE),
@@ -13694,17 +13705,9 @@ ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd)
else
{
/* Constraints proved insufficient, so we need to scan the table. */
- List *all_parts;
ListCell *lc;
- /* Take an exclusive lock on the partitions to be checked */
- if (attachrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
- all_parts = find_all_inheritors(RelationGetRelid(attachrel),
- AccessExclusiveLock, NULL);
- else
- all_parts = list_make1_oid(RelationGetRelid(attachrel));
-
- foreach(lc, all_parts)
+ foreach(lc, attachrel_children)
{
AlteredTableInfo *tab;
Oid part_relid = lfirst_oid(lc);