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Re: Query slow after analyse on postgresql 8.2

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Kaufhold, Christian (LFD)" <Christian(dot)Kaufhold(at)blfd(dot)bayern(dot)de>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Query slow after analyse on postgresql 8.2
Date: 2010-06-17 14:58:36
Message-ID: 3775.1276786716@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
"Kaufhold, Christian (LFD)" <Christian(dot)Kaufhold(at)blfd(dot)bayern(dot)de> writes:
> I have the following query that I run agains postgresql 8.2:
> ...
> But when I run analyse the same query runs for hours.

Seems like the core of the problem is here:

>                                                               ->  Seq
> Scan on massnahmeobjekt m  (cost=0.00..3271.88 rows=1 width=94) (actual
> time=0.387..577.771 rows=3694 loops=1)
> Filter: ((aktennummer)::text ~* 'M\\-2009\\-1'::text)

If that rowcount estimate weren't off by three orders of magnitude you
probably would be getting a more appropriate plan.  The first thing you
could try is increasing the statistics target for aktennummer.  Also,
if you're running in a non-C locale and this is 8.2.5 or older, try a
more recent 8.2.x.  Updating to 8.3 or 8.4 might help even more.

			regards, tom lane

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Subject: Re: Query slow after analyse on postgresql 8.2
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Subject: Re: Parallel queries for a web-application |performance testing

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