From: Tom Lane <tgl@sss.pgh.pa.us>
To: Franck Routier <franck.routier@axege.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: What happens between end of explain analyze and end of query execution ?
Date: Sat, 06 Apr 2013 12:27:21 -0400
Message-ID: <5541.1365265641@sss.pgh.pa.us> (raw)
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Franck Routier <franck.routier@axege.com> writes:
> Le 05/04/2013 16:17, Tom Lane a écrit :
>> What have you got the statistics targets set to in this database?
> Ok, the problem definitely comes from the default_statistics_target
> which is obviously too high on the database.
Yeah, eqjoinsel() is O(N^2) in the lengths of the MCV lists, in the
worst case where there's little overlap in the list memberships.
The actual cost would depend a lot on the specific column datatypes.
Not sure about your report that re-analyzing with the same stats target
made a significant difference. It might have been a matter of chance
variation in the sampled MCV list leading to more or fewer matches.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, franck.routier@axege.com
Subject: Re: What happens between end of explain analyze and end of query execution ?
In-Reply-To: <5541.1365265641@sss.pgh.pa.us>
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