On Sat, 2005-09-17 at 17:47 +0200, Antoine Bajolet wrote: > There are more tables around, but the heart of the search engine is > made of three tables : > > fiches (f_id int4, f_title varchar) 52445 rows > engine (f_id int4, k_id int4, weight ) 11761700 rows > keywords(k_id, keyword) 1072600 rows > > A "fiche" is linked to any kind of document. > The engine table counts how many times a keyword appears in a document. > > A query to search on one or two keywords is quick to execute (the > front-end creates thoses queries): >
> Is there a specific reason the planner chooses this way ? Yes, you have an additional join for each new keyword, so there is more work to do. Recode your SQL with an IN subselect that retrieves all possible keywords before it accesses the larger table. That way you should have only one join for each new keyword. > Can whe do something on the postgresql configuration to avoid this ? > Can whe force the planner to use a hash join as it does for the first > joins ? Not required, IMHO. Best Regards, Simon Riggs ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly