Re: [BUG] Fix DETACH with FK pointing to a partitioned table fails

I think  old "sub-FK" should not be dropped, that will be violates foreign
key constraint. For example :
postgres=# insert into r values(1,1);
INSERT 0 1
postgres=# ALTER TABLE r DETACH PARTITION r_1;
ALTER TABLE
postgres=# delete from p_1 where id = 1;
DELETE 1
postgres=# select * from r_1;
 id | p_id
----+------
  1 |    1
(1 row)

If I run above SQLs on pg12.12, it will report error below:
postgres=# delete from p_1 where id = 1;
ERROR:  update or delete on table "p_1" violates foreign key constraint
"r_1_p_id_fkey1" on table "r_1"
DETAIL:  Key (id)=(1) is still referenced from table "r_1".

Alvaro Herrera <alvherre@alvh.no-ip.org> 于2023年7月31日周一 20:58写道：

> On 2023-Jul-05, Jehan-Guillaume de Rorthais wrote:
>
> >   ALTER TABLE r ATTACH PARTITION r_1 FOR VALUES IN (1);
> >
> > The old sub-FKs (below 18289) created in this table to enforce the action
> > triggers on referenced partitions are not deleted when the table becomes
> a
> > partition. Because of this, we have additional and useless triggers on
> the
> > referenced partitions and we can not DETACH this partition on the
> referencing
> > side anymore:
>
> Oh, hm, interesting.  Thanks for the report and patch.  I found a couple
> of minor issues with it (most serious one: nkeys should be 3, not 2;
> also sysscan should use conrelid index), but I'll try and complete it so
> that it's ready for 2023-08-10's releases.
>
> Regards
>
> --
> Álvaro Herrera               48°01'N 7°57'E  —
> https://www.EnterpriseDB.com/
>
>
>