pgsql-general-owner@xxxxxxxxxxxxxx wrote: > On Tue, Jan 19, 2010 at 07:40:00AM +0100, Philippe Lang wrote: >> I'm trying to figure out how to use an index on an immutable function >> call in order to speed up queries. > [..] >> Unfortunately, Postgreql does not use the index at all. > > Yup, an index isn't going to be very useful in what you're doing. > It's arranged the "wrong" way around---you want something in the > table itself to compare against. I'd just have another column in the > table that stores the result of the function call (use a trigger to > keep it up to date) and then create an index on this column if you > want/need. Hi, I'm already doing "caching with triggers", it works great. The only problem is that it costs an extra "machinery": a column and triggers. I was wondering this morning if a proper index could replace this. It looks like the answer is "yes", but I'm worried about stability: you are never sure in advance how the planner will work exactly... Best regards, Philippe ----------------------------------------------------------------------- Philippe Lang Web : www.attiksystem.ch Attik System Email : philippe.lang@xxxxxxxxxxxxxx rte de la Fonderie 2 Phone : +41 26 422 13 75 1700 Fribourg Mobile : +41 79 351 49 94 Switzerland Fax : +41 26 422 13 76 -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
