On Tue, Aug 28, 2012 at 05:18:34PM +0200, Kohei KaiGai wrote: > 2012/8/28 David Fetter <da...@fetter.org>: > > On Tue, Aug 28, 2012 at 10:58:25AM -0400, Tom Lane wrote: > >> Kohei KaiGai <kai...@kaigai.gr.jp> writes: > >> > It seems to me TargetEntry of the parse tree can inform us > >> > which column should be modified on UPDATE or INSERT. If it has > >> > just a Var element that reference original table as-is, it > >> > means here is no change. > >> > >> Only if you're not going to support BEFORE triggers modifying the > >> row... > > > > +1 for supporting these. > > > > Speaking of triggers on foreign tables, what's needed to support > > them independent of support at the FDW level for writing on > > foreign tables, or does that even make sense? > > > I agree with trigger support on foreign tables is definitely useful > feature, even though it does not have capability to replace the > writable foreign table functionality.
With utmost respect, trigger support does make it possible to write to foreign tables using a whole-row comparison with the effect that all whole-row matches would be affected. This is how DBI-Link does it currently. > In case when foreign-table definition does not contain a column > mapped with primary-key column in remote-side, the trigger function > cannot determine which row should be updated / deleted. It is a > situation that FDW driver should track a particular remote-row using > its identifier. Generated identifiers and whole-row matching are two ways to approach this. There are likely others, especially in cases where people have special knowledge of the remote source. Cheers, David. -- David Fetter <da...@fetter.org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david.fet...@gmail.com iCal: webcal://www.tripit.com/feed/ical/people/david74/tripit.ics Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers