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From: Albe Laurenz <[email protected]>
To: 'fx TATEISHI KOJI  *EXTERN*' <[email protected]>
To: [email protected] <[email protected]>
Subject: Re: Performance degradation from PostgreSQL 8.2.21 to PostgreSQL 9.3.2
Date: Wed, 19 Jul 2017 06:46:43 +0000
Message-ID: <A737B7A37273E048B164557ADEF4A58B53A8464B@ntex2010i.host.magwien.gv.at> (raw)
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fx TATEISHI KOJI wrote:
> Issuing exactly the same query as PostgreSQL 8.2.21 and PostgreSQL 9.3.2 will slow the
> response by 6.4 ms on average.
> What could be the cause?
> Measurement method is as follows.
> ・ PostgreSQL 8.2.21 installation
>  ★Measurement
> ・ Export DUMP of PostgreSQL 8.2.21
> ・ PostgreSQL 8.2.21 uninstallation
> ・ PostgreSQL 9.3.2 installation
> ・ Dump import
>  ★Measurement

It is impossible to answer this with certainty without
EXPLAIN (ANALYZE, BUFFERS) output, but my first guess is that
the statistics on the 9.3 installation are not up to date.

ANALYZE all involved tables, then try again and see if the
performance degradation has vanished.

If not, start studying the execution plans.

Are the parameters in postgresql.conf set the same?

Yours,
Laurenz Albe

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