Re: Very big insert/join performance problem (bacula)

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Marc Cousin" <cousinmarc(at)gmail(dot)com>
Cc: "Alvaro Herrera" <alvherre(at)alvh(dot)no-ip(dot)org>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Very big insert/join performance problem (bacula)
Date: 2009-07-16 22:30:17
Message-ID: 4A5F63A902000025000288B6@gw.wicourts.gov
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Marc Cousin <cousinmarc(at)gmail(dot)com> wrote:

> As mentionned in another mail from the thread (from Richard Huxton),
> I felt this message in the documentation a bit misleading :
>
> effective_cache_size (integer)
> Sets the planner's assumption about the effective size of the disk
> cache that is available to a single query
>
> I don't really know what the 'a single query' means. I interpreted
> that as 'divide it by the amount of queries typically running in
> parallel on the database'. Maybe it should be rephrased ? (I may not
> be the one misunderstanding it).

I'm afraid I'll have to let someone else speak to that; I only have a
vague sense of its impact. I've generally gotten good results setting
that to the available cache space on the machine. If I'm running
multiple database clusters on one machine, I tend to hedge a little
and set it lower to allow for some competition.

-Kevin

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