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

Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> 于2024年10月25日周五 23:14写道：

> On 2024-Oct-25, Alexander Lakhin wrote:
>
> > I've also discovered another anomaly with a similar setup, but it's not
> > related to 53af9491a.
>
> Hmm, it may well be a preexisting problem, but I do think it involves
> the same code. As far as I can tell, the value "2" here
>
> > This script ends up with:
> > ERROR: invalid attribute number 2
> > ERROR: cache lookup failed for attribute 2 of relation 16398
>
> is coming from riinfo->confdelsetcols which was set up by
> DetachPartitionFinalize during the last DETACH operation.
>

Hmm, actually, the confdelsetcols before detach and after detach is always
{2}, as below:

postgres=# select oid, conname, conrelid,conparentid,confdelsetcols from
pg_constraint where conrelid = 16397;
oid | conname | conrelid | conparentid | confdelsetcols
-------+-----------+----------+-------------+----------------
16400 | pt_a_fkey | 16397 | 16392 | {2}
(1 row)

postgres=# ALTER TABLE pt DETACH PARTITION tp1;
ALTER TABLE
postgres=# select oid, conname, conrelid,conparentid,confdelsetcols from
pg_constraint where conrelid = 16397;
oid | conname | conrelid | conparentid | confdelsetcols
-------+-----------+----------+-------------+----------------
16400 | pt_a_fkey | 16397 | 0 | {2}
(1 row)

Even though no detach, the confdelsetcols is {2} . But no error report.
Because the rel->rd_att->natts of pt is 2.
It will not go into tp1 because tp1 is a partition of pt. But after
detach, the rel->rd_att->natts of tp1 is 1,
so "ERROR: invalid attribute number 2" will report.

CREATE TABLE tp1... will ignore the dropped column of parent, so the natts
of tp1 is 1, but its parent is 2.

--
Thanks,
Tender Wang