| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Jean-Philippe Côté <jean-philippe(dot)cote(at)crt(dot)umontreal(dot)ca> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Extremely irregular query performance |
| Date: | 2006-01-12 03:23:55 |
| Message-ID: | 480.1137036235@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
=?iso-8859-1?Q?Jean-Philippe_C=F4t=E9?= <jean-philippe(dot)cote(at)crt(dot)umontreal(dot)ca> writes:
> Thanks a lot for this info, I was indeed exceeding the genetic
> optimizer's threshold. Now that it is turned off, I get
> a very stable response time of 435ms (more or less 5ms) for
> the same query. It is about three times slower than the best
> I got with the genetic optimizer on, but the overall average
> is much lower.
Hmm. It would be interesting to use EXPLAIN ANALYZE to confirm that the
plan found this way is the same as the best plan found by GEQO, and
the extra couple hundred msec is the price you pay for the exhaustive
plan search. If GEQO is managing to find a plan better than the regular
planner then we need to look into why ...
regards, tom lane
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