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To: "Jim C. Nasby" <decibel@decibel.org>
Cc: Michael Stone <mstone+postgres@mathom.us>,
 pgsql-performance@postgresql.org
Subject: Re: [doc patch] a slight VACUUM / VACUUM FULL doc improvement
 proposal
References: <87lkfqavg9.fsf@meuh.mnc.lan> <20070515174427.GG1785@mathom.us>
	<87hcqdb4g5.fsf@meuh.mnc.lan> <20070516154809.GL14548@nasby.net>
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From: Guillaume Cottenceau <gc@mnc.ch>
Date: 16 May 2007 18:00:19 +0200
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"Jim C. Nasby" <decibel 'at' decibel.org> writes:

> On Wed, May 16, 2007 at 09:41:46AM +0200, Guillaume Cottenceau wrote:

[...]

> > Come on, I don't suggest to remove several bold warnings about
> > it, the best one being "Therefore, frequently using VACUUM FULL
> > can have an extremely negative effect on the performance of
> > concurrent database queries." My point is to add the few
> > additional mentions; I don't think the claims that VACUUM FULL
> > physically compacts the data, and might be useful in case of too
> > long time with infrequent VACUUM are incorrect, are they?
> 
> Unfortunately they are, to a degree. VACUUM FULL can create a
> substantial amount of churn in the indexes, resulting in bloated
> indexes. So often you have to REINDEX after you VACUUM FULL.

Ok, VACUUM FULL does his job (it physically compacts the data and
might be useful in case of too long time with infrequent VACUUM),
but we are going to not talk about it because we often needs a
REINDEX after it? The natural conclusion would rather be to
document the fact than REINDEX is needed after VACUUM FULL, isn't
it?

-- 
Guillaume Cottenceau, MNC Mobile News Channel SA, an Alcatel-Lucent Company
Av. de la Gare 10, 1003 Lausanne, Switzerland - direct +41 21 317 50 36