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

On Thu, 3 Aug 2023 11:02:43 +0200
Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:

> On 2023-Aug-03, tender wang wrote:
>
> > I think old "sub-FK" should not be dropped, that will be violates foreign
> > key constraint.
>
> Yeah, I've been playing more with the patch and it is definitely not
> doing the right things. Just eyeballing the contents of pg_trigger and
> pg_constraint for partitions added by ALTER...ATTACH shows that the
> catalog contents are inconsistent with those added by CREATE TABLE
> PARTITION OF.

Well, as stated in my orignal message, at the patch helps understanding the
problem and sketch a possible solution. It definitely is not complete.

After DETACHing the table, we surely needs to check everything again and
recreating what is needed to keep the FK consistent.

But should we keep the FK after DETACH? Did you check the two other discussions
related to FK, self-FK & partition? Unfortunately, as Tender experienced, the
more we dig the more we find bugs. Moreover, the second one might seems
unsolvable and deserve a closer look. See:

* FK broken after DETACHing referencing part
https://www.postgresql.org/message-id/20230420144344.40744130%40karst
* Issue attaching a table to a partitioned table with an auto-referenced
foreign key
https://www.postgresql.org/message-id/20230707175859.17c91538%40karst