Hi Sylvain, Might sound like a nasty question, and gurus will correct me if I'm wrong, but first thing to investigate is why the index is not used : - You have 2/3 million rows per table so the planner should use the index. Seqscan is prefered for small tables. - Maybe the WHERE clause of your DELETE statement doesn't make use of your start and end date columns ? If so, in which order ?
Please, provide with your Pg version and the table setup with the index. Regards, Sekine 2012/10/16 Sylvain CAILLET <scail...@alaloop.com> > Hi to all, > > I've got a trouble with some delete statements. My db contains a little > more than 10000 tables and runs on a dedicated server (Debian 6 - bi quad > - 16Gb - SAS disks raid 0). Most of the tables contains between 2 and 3 > million rows and no foreign keys exist between them. Each is indexed > (btree) on start_date / end_date fields (bigint). The Postgresql server has > been tuned (I can give modified values if needed). > > I perform recurrent DELETE upon a table subset (~1900 tables) and each > time, I delete a few lines (between 0 and 1200). Usually it takes between > 10s and more than 2mn. It seems to me to be a huge amount of time ! An > EXPLAIN ANALYZE on a DELETE shows me that the planner uses a Seq Scan > instead of an Index Scan. Autovaccum is on and I expect the db stats to be > updated in real time (pg_stats file is stored in /dev/shm RAM disk for > quick access). > > Do you have any idea about this trouble ? > > Sylvain Caillet > Bureau : + 33 5 59 41 51 10 > scail...@alaloop.com > > ALALOOP S.A.S. - Technopole Izarbel - 64210 Bidart > www.alaloop.com > >
