On 11/26/2008 03:20 PM, Scott Marlowe wrote: > On Tue, Nov 25, 2008 at 10:22 PM, Clemens Schwaighofer > <clemens.schwaighofer@xxxxxxxxxx> wrote: >> On 11/26/2008 02:15 PM, Scott Marlowe wrote: >>> Are there more rows in the 8.2 table you're testing on? Or is the >>> whole table small enough to fit on a few pages? >> I highly doubt that. I have right now in one of the DBs I transfered >> tables from ~100.000 down to ~40.000 rows that all join together. I >> somehow really doubt that fit in a few pages. > > Right, with more rows, and choosing fewer, pgsql will go for an index > scan. if choosing a good %, the seq scan. okay, then I think I get it. One of my test queries was actually selecting a very big chunk (90%) of the data, so it makes sense the planner chooses seq scan over index scan here. >> So, I am fine when I trust the Postgresql planner :) Because speed wise >> I see no difference that 8.3 would be slower than 8.2 > > Well, the planner's not perfect. Some off corner cases can catch it > out, or if your database isn't analyzed after a lot of changes it may > make an uninformed decision. But most the time it makes the right, or > close enough, decision. Well, I have autovacuum turned on, so this should hopefully keep the planner up to date. Anyway, thanks a lot for your help. -- [ Clemens Schwaighofer -----=====:::::~ ] [ IT Engineer/Manager ] [ E-Graphics Communications, TEQUILA\ Japan IT Group ] [ 6-17-2 Ginza Chuo-ku, Tokyo 104-8167, JAPAN ] [ Tel: +81-(0)3-3545-7706 Fax: +81-(0)3-3545-7343 ] [ http://www.tequila.jp ]
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