On Tue, May 5, 2015 at 9:36 AM, Andres Freund <and...@anarazel.de> wrote: > Theoretically this changes the pictures for FDWs, right? Right now > there's > + <para> > + <command>INSERT</> with an <literal>ON CONFLICT</> clause is not > + supported with a unique index inference specification, since a > + conflict arbitrating unique index cannot meaningfully be inferred > + on a foreign table (this implies that <literal>ON CONFLICT DO > + UPDATE</> is never supported, since the specification is > + mandatory there). > + </para> > but theoretically the constraint name could be meaningful on the other > side...
Well, the inference clause could be too -- in that sense, the constraint name isn't special at all. But you need to invent a way of making the optimizer infer an index on the foreign side (and even with a named constraint, we go from constraint Oid in the parser to pg_index Oid in the optimizer, so it's a similar process to regular inference). Of course, teaching the optimizer about foreign indexes is a whole new infrastructure. Note that this really is the explanation for why postgres_fdw only has limited support. Sure, I haven't added deparsing logic for ON CONFLICT UPDATE, but it would be pretty easy to do so, and that isn't the blocker at all. > I don't think this is anyting for 9.5, but it might be interesting for > later. Sure. -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
