Cc: pgsql-performance@postgresql.org
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Date: Tue, 18 Dec 2012 15:09:54 -0500
From: "Kevin Grittner" <kgrittn@mail.com>
Message-ID: <20121218200955.14720@gmx.com>
MIME-Version: 1.0
Subject: Re: Slow queries after vacuum analyze
To: "Ghislain ROUVIGNAC" <ghr@sylob.com>
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Ghislain ROUVIGNAC wrote:

> Memory : In use 4 Go, Free 15Go, cache 5 Go.

If the active portion of your database is actually small enough
that it fits in the OS cache, I recommend:

seq_page_cost = 0.1
random_page_cost = 0.1
cpu_tuple_cost = 0.05

> I plan to increase various parameters as follow:
> shared_buffers = 512MB
> temp_buffers = 16MB
> work_mem = 32MB
> wal_buffers = 16MB
> checkpoint_segments = 32
> effective_cache_size = 2560MB
> default_statistics_target = 500
> autovacuum_vacuum_scale_factor = 0.05
> autovacuum_analyze_scale_factor = 0.025

You could probably go a little higher on work_mem and
effective_cache_size. I would leave default_statistics_target alone
unless you see a lot of estimates which are off by more than an
order of magnitude. Even then, it is often better to set a higher
value for a few individual columns than for everything. Remember
that this setting has no effect until you reload the configuration
and then VACUUM.

-Kevin


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