Robert, On Mon, Oct 5, 2009 at 11:01 PM, Robert Haas <robertmhaas@xxxxxxxxx> wrote: > On Sun, Oct 4, 2009 at 9:58 PM, Omar Kilani <omar.kilani@xxxxxxxxx> wrote: >> Hi Xia, >> >> Try this patch: >> >> http://treehou.se/~omar/postgresql-8.4.1-array_sel_hack.patch >> >> It's a hack, but it works for us. I think you're probably spending >> most of your query time planning, and this patch helps speed things up >> 10x over here. > > Woof. I can see that helping in some situations, but what a foot-gun! We've run that patch for about 4 years (originally coded for us by Neil Conway for 8.2, I think), and have never seen any negatives from it. I'm not really sure what the alternatives are -- it never really makes sense to get the selectivity for thousands of items in the IN clause. I've never seen a different plan for the same query against a DB with that patch vs without -- it just takes a huge amount of time longer to run without it. :) But yeah, definitely a hack, and should only be used if needed -- hopefully there's some sort of official solution on the horizon. :) > ...Robert Regards, Omar -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
