Re: Several issues with postgres_fdw stats import

On Tue, Sep 15, 2026 at 8:31 PM Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com> wrote:
> On Tue, Sep 15, 2026 at 5:52 PM Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> > When I used v11 as the remote server, stats import via postgres_fdw
> > resulted in the following error. I think this should be addressed as well.
> >
> > ERROR: collations are not supported by type name
> > CONTEXT: remote SQL command: SELECT DISTINCT ON (attname COLLATE "C")
> > attname, null_frac, avg_width, n_distinct, most_common_vals,
> > most_common_freqs, histogram_bounds, correlation, most_common_elems,
> > most_common_elem_freqs, elem_count_histogram, NULL, NULL, NULL FROM
> > pg_catalog.pg_stats WHERE schemaname = 'public' AND tablename = 't'
> > AND attname = ANY(ARRAY['i', 'j']) ORDER BY attname COLLATE "C",
> > inherited DESC
>
> Reproduced here. Will fix.

As the error message says, the cause of this is that the name type
isn't collatable in v11. It was made so in v12, so I fixed this by
just s/attname COLLATE "C"/attname::text COLLATE "C"/ to the query
generated for v11 or older.

Also, I fixed another bug in the same function: a typo in the if-test
to check whether the remote server is v9.2 or later. The if-test in
Corey's original version was correct, so that's my fault when updating
it to the current version. :palmface:

Attached is a patch for that.

Best regards,
Etsuro Fujita