On Tue, 2008-09-02 at 12:28 -0400, Tom Lane wrote: > Simon Riggs <[EMAIL PROTECTED]> writes: > > As discussed on 26 June, "Join Removal/Vertical Partitioning", here's a > > patch to remove joins in certain circumstances. > > Some points not made in the thread so far:
Various comments accepted and agreed. > > + * XXX Seems not worth searching partial indexes > > because those > > + * are only usable with a appropriate restriction, so > > the > > + * only way they could ever be usable is if there was a > > + * restriction that exactly matched the index predicate, > > + * which is possible but generally unlikely. > > I haven't thought this through entirely, but wouldn't a partial index be > okay if it's marked predOK? You might be right that the case is > unlikely, but if it's only one extra line to support it ... As of now, its it is predOK then that implies there was a qual on the checkrel so can't remove the join. So no need to check. > > + if (removable && > > + joinrel->cheapest_total_path < keeprel->cheapest_total_path) > > This test on cheapest_total_path seems pretty wacko and stuff below it definitely is, from upthread discussion. Hang fire on more comments - its a short patch but needs a few thwacks from the cluestick yet before next review. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-patches mailing list (pgsql-patches@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-patches
