Re: Slower query after psql changed it's execution plan

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Romuald Brunet <romuald(dot)brunet(at)gmail(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Slower query after psql changed it's execution plan
Date: 2009-03-23 14:26:38
Message-ID: 8646.1237818398@sss.pgh.pa.us
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Romuald Brunet <romuald(dot)brunet(at)gmail(dot)com> writes:
> After some investigation, we found out that the PostgreSQL server
> (8.1) changed the execution plan (I'm assuming because the number of
> rows increased).

The problem seems to be that the estimate for the number of rows fetched
from dc_post changed drastically --- it was in the right ballpark, and
now it's off by a factor of 30. Why is that? Maybe you had had a
special statistics target setting, and it got dropped?

> The statistics are at the default value everywhere (10)

Almost certainly not enough.

regards, tom lane

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