To: Michael Stone <mstone+postgres@mathom.us>
Cc: 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>
From: Guillaume Cottenceau <gc@mnc.ch>
Date: 16 May 2007 09:41:46 +0200
In-Reply-To: <20070515174427.GG1785@mathom.us>
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Michael Stone <mstone+postgres 'at' mathom.us> writes:

> On Tue, May 15, 2007 at 06:43:50PM +0200, Guillaume Cottenceau wrote:
> >patch - basically, I think the documentation under estimates (or
> >sometimes misses) the benefit of VACUUM FULL for scans, and the
> >needs of VACUUM FULL if the routine VACUUM hasn't been done
> >properly since the database was put in production.
> 
> It's also possible to overestimate the benefit of vacuum full, leading
> to people vacuum full'ing almost constantly, then complaining about
> performance due to the associated overhead. I think there have been
> more people on this list whose performance problems were caused by
> unnecessary full vacs than by those whose performance problems were
> caused by insufficient full vacs.

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?

-- 
Guillaume Cottenceau, MNC Mobile News Channel SA, an Alcatel-Lucent Company
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