Re: Optimize update query

From: Shaun Thomas <sthomas(at)optionshouse(dot)com>
To: Niels Kristian Schjødt <nielskristian(at)autouncle(dot)com>
Cc: Kevin Grittner <kgrittn(at)mail(dot)com>, Willem Leenen <willem_leenen(at)hotmail(dot)com>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Optimize update query
Date: 2012-11-30 13:49:08
Message-ID: 50B8B954.7060807@optionshouse.com
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On 11/30/2012 07:31 AM, Niels Kristian Schjødt wrote:

> In theory what difference should it make to the performance, to have
> a pool in front of the database, that all my workers and web servers
> connect to instead of connecting directly? Where is the performance
> gain coming from in that situation?

If you have several more connections than you have processors, the
database does a *lot* more context switching, and among other things,
that drastically reduces PG performance. On a testbed, I can get over
150k transactions per second on PG 9.1 with a 1-1 relationship between
CPU and client. Increase that to a few hundred, and my TPS drops down to
30k. Simply having the clients there kills performance.

--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-444-8534
sthomas(at)optionshouse(dot)com

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