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Date: Fri, 10 Mar 2006 03:48:26 -0700
From: Michael Fuhr <mike@fuhr.org>
To: Ruben Rubio Rey <ruben@rentalia.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Query time
Message-ID: <20060310104826.GA14532@winnie.fuhr.org>
References: <44114F85.8020702@rentalia.com>
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On Fri, Mar 10, 2006 at 11:05:57AM +0100, Ruben Rubio Rey wrote:
> Sometimes some big query takes between 5 to 15 seconds. It happens 
> sometimes all the day it does not depend if database is busy.
> 
> I have measured that sentence in 15 - 70 ms in normal circunstances.

Is it the *exact* same query, including the values you're querying
for?  The same query with different values can run with different
plans depending on row count estimates.  It might be useful to see
the query string and the EXPLAIN ANALYZE output for a fast query
and a slow one.

How many tables are you querying?  Might you be hitting geqo_threshold
(default 12)?  If so then the following thread might be helpful:

http://archives.postgresql.org/pgsql-performance/2006-01/msg00132.php

-- 
Michael Fuhr