From: Tom Lane <tgl@sss.pgh.pa.us>
To: Bruno Baguette <bruno.baguette@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Slow SQL query (14-15 seconds)
Date: Thu, 13 Nov 2008 08:31:50 -0500
Message-ID: <5163.1226583110@sss.pgh.pa.us> (raw)
In-Reply-To: <491C0962.9060405@gmail.com>
References: <491C0962.9060405@gmail.com>
Bruno Baguette <bruno.baguette@gmail.com> writes:
> I'm having a problem with this query (below) that takes betweend 14 and
> 15 seconds to run, which is too long for the end-user.
> I've done a EXPLAIN ANALYZE (below below) but I'm having difficulties to
> see which part of that query is taking so many times.
It's the repeatedly executed EXISTS subplan that's hurting you:
> SubPlan
> -> Nested Loop (cost=35.56..378.16
> rows=2 width=0) (actual time=16.511..16.511 rows=0 loops=818)
16.511 * 818 = 13505.998, so this is all but about 100 msec of the
runtime. Can't tell if there's any easy way to improve it. In
pre-8.4 releases trying to convert the EXISTS into an IN might help.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, bruno.baguette@gmail.com
Subject: Re: Slow SQL query (14-15 seconds)
In-Reply-To: <5163.1226583110@sss.pgh.pa.us>
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