We are running Postgresql 8.1, and getting dramatically inconsistant results
after running VACUUM ANALYZE. Sometimes after analyzing the database, the
query planner chooses a very efficient plan (15 rows, 4.744 ms), and
sometimes a terrible one (24 rows, 3536.995 ms). Here's the abbreviated
SELECT * FROM t1 INNER JOIN (t2 INNER JOIN (t3 INNER JOIN t4 ON t3.gid =
t4.gid) ON t3.gid = t2.gid) ON t2.eid = t1.eid WHERE ...
In the efficient plan, t2 is joined to t3 & t4 before being joined to t1.
The inefficient plan joins t1 to t2 before joining to the other tables.
We've experimented with different settings, such as shared_buffers &
max_fsm_pages, to no avail. Anybody have a suggestion for getting the
efficient plan to execute consistantly? If you'd like to see the actual
query & query plans let me know.
pgsql-performance by date
|Next:||From: Scott Marlowe||Date: 2006-01-24 23:30:18|
|Subject: Re: Inconsistant query plan|
|Previous:||From: Andrew Sullivan||Date: 2006-01-24 21:00:37|
|Subject: Re: Investigating IO Saturation|