2011/3/16 Tomas Vondra <tv@xxxxxxxx>: > Dne 16.3.2011 21:38, Davenport, Julie napsal(a): >> OK, I did the explain analyze on both sides (using a file for output instead) and used the tool you suggested. >> >> 8.0 - http://explain.depesz.com/s/Wam >> 8.4 - http://explain.depesz.com/s/asJ > > Great, that's exactly what I asked for. I'll repost that to the mailing > list so that the others can check it too. > >> When I run the queries I get 59,881 rows on the 8.0 side and 59,880 on the 8.4 side, which is what I expect because 8.4 side was updated a couple hours later and some minor changes make sense. > > Hm, obviously both versions got the row estimates wrong, but the 8.4 > difference (200x) is much bigger that the 8.0 (10x). This might be one > of the reasons why a different plan is chosen. the expression to_char(course_begin_date, 'YYYYMMDD'::text) = '20101025'::text should be a problem much better is test on equality in date domain like: course_begin_date = to_date('20101025', 'YYYYMMDD') this is faster and probably better estimated Regards Pavel Stehule -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
