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To: Craig James <craig_james@emolecules.com>
cc: pgsql-performance@postgresql.org
Subject: Re: Auto-ANALYZE? 
In-reply-to: <4654D26E.1020208@emolecules.com> 
References: <4654D26E.1020208@emolecules.com>
Comments: In-reply-to Craig James <craig_james@emolecules.com>
	message dated "Wed, 23 May 2007 16:46:54 -0700"
Date: Wed, 23 May 2007 19:55:58 -0400
Message-ID: <26268.1179964558@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Craig James <craig_james@emolecules.com> writes:
> Auto-vacuum has made Postgres a much more "friendly" system.  Is there some reason the planner can't also auto-ANALYZE in some situations?

autovacuum handles analyze too.  Trying to make the planner do it is
a crummy idea for a couple of reasons:

* unpredictable performance if queries sometimes go off for a few
  seconds to collect stats
* pg_statistics update requires semi-exclusive lock
* work is lost if transaction later rolls back

			regards, tom lane