Re: [HACKERS] Varying results when using merge joins overpostgres_fdw vs hash joins

I'm not sure whether there's a way to fix this that doesn't break other
cases.  We could retrieve the pg_database.datcollate string from the
remote, but that doesn't necessarily match up with any collation name
we know about locally.  One pretty common failure mode would be that
the datcollate string isn't a canonical spelling (eg, "en_US.UTF-8"
where the name we know about is "en_US.utf8").  In general, datcollate
is handled through other code paths than collation names, so it might
easily be that it doesn't match anything in the remote's pg_collation
catalog either :-(.