Subject: Re: Doc patch for truncate.sgml
From: Devrim =?ISO-8859-1?Q?G=DCND=DCZ?= <devrim@gunduz.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Peter Eisentraut <peter_e@gmx.net>, pgsql-docs <pgsql-docs@postgresql.org>
In-Reply-To: <26043.1219947627@sss.pgh.pa.us>
References: <1219936487.3376.14.camel@laptop.gunduz.org>
	<48B6E0A6.7030201@gmx.net>  <26043.1219947627@sss.pgh.pa.us>
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Date: Thu, 28 Aug 2008 21:48:18 +0300
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Hi,

On Thu, 2008-08-28 at 14:20 -0400, Tom Lane wrote:
> > If the table is in fact empty, why is it a bad idea to let the=20
> > statistics reflect that?
>=20
> I think that this thinking is at least partially obsolete now that
> autovacuum/autoanalyze and plan invalidation are in place.  It used to
> be that if you truncated a table and then filled it again, any cached
> plans that were made while the table was really small would tend to
> suck when used with the re-filled table.  But now, autovac will launch
> (at least) an ANALYZE against any table that's grown materially, and
> the commit of the new analyze stats will result in invalidating any
> cached plans.  So the system should be capable of auto-tuning its
> plans to changes in table size ... not instantaneously of course, but
> then you can't fill a big table instantaneously either.

Good point.

--=20
Devrim G=C3=9CND=C3=9CZ, RHCE
devrim~gunduz.org, devrim~PostgreSQL.org, devrim.gunduz~linux.org.tr
                   http://www.gunduz.org

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