Re: Varying results when using merge joins over postgres_fdw vs hash joins

>
>
> The collation column is empty here, which means that collation for
> str* columns is default collation i.e. C. This isn't true, since the
> default ncollation on the foreign server is different from the default
> collation of local database. AFAIU, import foreign schema should have
> set appropriate collation of the foreign table.
>

That's what we saw. The query inside IMPORT FOREIGN SCHEMA assumes a NULL
collation means default, without asking the server what that default is. I
was thinking that we could change the select
inside postgresImportForeignSchema and replace
collname,
with something borrowed from information_schema.sql like

coalesce(collname, (SELECT encoding FROM pg_catalog.pg_database
WHERE datname = pg_catalog.current_database()))

which itself isn't right because encoding names don't match up perfectly
with collation names.