From c7d43c4d8a5b7215ea0a32d95260188b5d3ae3f4 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Fri, 12 Oct 2018 12:36:26 -0300 Subject: Correct attach/detach logic for FKs in partitions There was no code to handle foreign key constraints on partitioned tables in the case of ALTER TABLE DETACH; and if you happened to ATTACH a partition that already had an equivalent constraint, that one was ignored and a new constraint was created. Adding this to the fact that foreign key cloning reuses the constraint name on the partition instead of generating a new name (as it probably should, to cater to SQL standard rules about constraint naming within schemas), the result was a pretty poor user experience -- the most visible failure was that just detaching a partition and re-attaching it failed with an error such as ERROR: duplicate key value violates unique constraint "pg_constraint_conrelid_contypid_conname_index" DETAIL: Key (conrelid, contypid, conname)=(26702, 0, test_result_asset_id_fkey) already exists. because it would try to create an identically-named constraint in the partition. To make matters worse, if you tried to drop the constraint in the now-independent partition, that would fail because the constraint was still seen as dependent on the constraint in its former parent partitioned table: ERROR: cannot drop inherited constraint "test_result_asset_id_fkey" of relation "test_result_cbsystem_0001_0050_monthly_2018_09" This fix attacks the problem from two angles: first, when the partition is detached, the constraint is also marked as independent, so the drop now works. Second, when the partition is re-attached, we scan existing constraints searching for one matching the FK in the parent, and if one exists, we link that one to the parent constraint. So we don't end up with a duplicate -- and better yet, we don't need to scan the referenced table to verify that the constraint holds. To implement this I made a small change to previously planner-only struct ForeignKeyCacheInfo to contain the constraint OID; also relcache now maintains the list of FKs for partitioned tables too. Backpatch to 11. Reported-by: Michael Vitale (bug #15425) Discussion: https://postgr.es/m/15425-2dbc9d2aa999f816@postgresql.org --- src/backend/nodes/copyfuncs.c | 1 + 1 file changed, 1 insertion(+) (limited to 'src/backend/nodes/copyfuncs.c') diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c index e47641d5721..e8ea59e34af 100644 --- a/src/backend/nodes/copyfuncs.c +++ b/src/backend/nodes/copyfuncs.c @@ -4745,6 +4745,7 @@ _copyForeignKeyCacheInfo(const ForeignKeyCacheInfo *from) { ForeignKeyCacheInfo *newnode = makeNode(ForeignKeyCacheInfo); + COPY_SCALAR_FIELD(conoid); COPY_SCALAR_FIELD(conrelid); COPY_SCALAR_FIELD(confrelid); COPY_SCALAR_FIELD(nkeys); -- cgit v1.2.3