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From: Ed Tyrrill <tyrrill_ed(at)emc(dot)com>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re:
Date: 2007-06-25 23:39:02
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Mon, 2007-06-25 at 17:56 -0400, Stephen Frost wrote:
> Was the 'work_mem' set to the same thing on all these runs?  Also, you
> might try increasing the 'work_mem' under 8.2.4, at least for this query
> (you can set it by just doing: set work_mem = '2GB'; or similar in psql,
> or you can change the default in postgresql.conf).
> The big thing of note, it seems, is that you've got enough memory and
> it's coming out faster when doing a hash-join vs. a sort + merge-join.
> Could likely be because it doesn't think there's enough work memory
> available for the hash, which might change based on the values it gets
> from the statistics on how frequently something shows up, etc.
> 	Enjoy,
> 		Stephen

Yes, work_mem was set to 128MB for all runs.  All settings were the same
except for the change to default_statistics_target.  I'm certainly
memory constrained, but giving 2GB to one one session doesn't allow
other sessions to do anything.  Possibly when we upgrade to 16GB. :-)

In response to

  • Re: at 2007-06-25 21:56:54 from Stephen Frost


  • Re: at 2007-06-25 23:52:09 from Stephen Frost

pgsql-performance by date

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Subject: Re: startup caching suggestions

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