From: Philip Scott <pscott@foo.me.uk>
To: 'Claudio Freire' <klaussfreire@gmail.com>
To: postgresql@foo.me.uk
Cc: 'postgres performance list' <pgsql-performance@postgresql.org>
Subject: Re: Slow query: bitmap scan troubles
Date: Tue, 4 Dec 2012 18:31:05 -0000
Message-ID: <098101cdd24d$892524c0$9b6f6e40$@foo.me.uk> (raw)
In-Reply-To: <CAGTBQpaKOfZs+qy+S7CCPcTg7PYOrwgcQAXgWV88cQTn-BFstg@mail.gmail.com>
References: <092a01cdd230$ff6143c0$fe23cb40$@foo.me.uk>
<CAGTBQpaKOfZs+qy+S7CCPcTg7PYOrwgcQAXgWV88cQTn-BFstg@mail.gmail.com>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-performance>
> The difference between cost estimation and actual cost of your queries,
under relatively precise row estimates, seems to suggest your e_c_s or r_p_c
aren't a reflection of your hardware's performance.
Wow, so tweaking these has fixed it and then some. It now picks a slightly
different plan than the 'fast' one previously:
New super fast version with e_c_s 6GB->88Gb and r_p_c 2-> 1 (s_p_c 1->0.5):
http://explain.depesz.com/s/ECk
For reference:
> Slow version with bitmapscan enabled: http://explain.depesz.com/s/6I7
> Fast version with bitmapscan disabled: http://explain.depesz.com/s/4MWG
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To: pgsql-performance@postgresql.org
Cc: pscott@foo.me.uk, klaussfreire@gmail.com, postgresql@foo.me.uk
Subject: Re: Slow query: bitmap scan troubles
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