Re: BUG: PostgreSQL 19devel throws internal opfamily error for FK with reordered referenced columns

On Fri, Apr 10, 2026 at 3:13 AM Matheus Alcantara
<matheusssilv97(at)gmail(dot)com> wrote:
> On Thu Apr 9, 2026 at 12:27 PM -03, Fredrik Widlert wrote:
> > Hello,
> >
> > I believe I may have found a regression in PostgreSQL 19devel, downloaded
> > on 2026-04-09
> > from https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.gz.
> >
> > postgres=# select version();
> > version
> > -----------------------------------------------------------------------------------------------------
> > PostgreSQL 19devel on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu
> > 13.2.0-23ubuntu4) 13.2.0, 64-bit
> >
> >
> > With the reproducer below, PostgreSQL 18 reports a normal foreign-key
> > violation
> > at INSERT time, but PostgreSQL 19devel instead throws an internal-looking
> > error:
> >
> > ERROR: operator 98 is not a member of opfamily 1976
> > -- reproducer:
> > drop table if exists parent, child;
> >
> > create table parent (
> > app_id varchar(256) not null,
> > report_id smallint not null,
> > otype integer not null,
> > subtype integer not null,
> > ctype integer not null,
> > column_name varchar(30) not null,
> > primary key (app_id, report_id, otype, subtype, ctype, column_name)
> > );
> >
> > create table child (
> > app_id varchar(256) not null,
> > report_id smallint not null,
> > otype integer not null,
> > subtype integer not null,
> > column_name varchar(30) not null,
> > ctype integer,
> > -- intentionally swapped: column_name, ctype
> > constraint child_fk
> > foreign key (app_id, report_id, otype, subtype, column_name, ctype)
> > references parent (app_id, report_id, otype, subtype, column_name,
> > ctype)
> > );
> >
> >
> > -- trigger the problem
> > insert into child (app_id, report_id, otype, subtype, column_name, ctype)
> > values ('DEFAULT_APP', 0, -1, -1, 'ID', -1);
> >
>
> Hi, thanks for reporting the issue.
>
> This seems to be related to commit 2da86c1ef9b. The issue is that in
> ri_populate_fastpath_metadata, the code uses idx_rel->rd_opfamily[i]
> where i is the constraint key position, but it should find the actual
> index column position for pk_attnums[i]. When FK columns are in a
> different order than PK columns, the constraint key position doesn't
> match the index column position.
>
> I didn't participate in the discussion of the feature but I studied the
> code a little bit after it was committed, so I'm taking a try to fix
> this issue with the attached patch, which seems to work for this case.
>
> CC Junwang Zhao and Amit Langote since they are involved in the original
> commit.

Thanks for the patch and for notifying me.

I will look at your patch later today, but in the meantime, I've added
an open item for this:
https://wiki.postgresql.org/wiki/PostgreSQL_19_Open_Items

--
Thanks, Amit Langote