From: Jim C. Nasby <decibel@decibel.org>
To: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Guillaume Cottenceau <gc@mnc.ch>
Cc: Michael Stone <mstone+postgres@mathom.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: [doc patch] a slight VACUUM / VACUUM FULL doc improvement proposal
Date: Wed, 16 May 2007 11:17:02 -0500
Message-ID: <20070516161702.GN14548@nasby.net> (raw)
In-Reply-To: <20070516160926.GX4582@alvh.no-ip.org>
References: <87lkfqavg9.fsf@meuh.mnc.lan>
<20070515174427.GG1785@mathom.us>
<87hcqdb4g5.fsf@meuh.mnc.lan>
<20070516154809.GL14548@nasby.net>
<877ir892ss.fsf@meuh.mnc.lan>
<20070516160926.GX4582@alvh.no-ip.org>
On Wed, May 16, 2007 at 12:09:26PM -0400, Alvaro Herrera wrote:
> Guillaume Cottenceau wrote:
> > "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?
>
> Maybe, but we should also mention that CLUSTER is a likely faster
> workaround.
What this boils down to is that there should probably be a separate
subsection that deals with "Oh noes! My tables are too big!"
--
Jim Nasby decibel@decibel.org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
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To: pgsql-performance@postgresql.org
Cc: decibel@decibel.org, alvherre@commandprompt.com, gc@mnc.ch, mstone+postgres@mathom.us
Subject: Re: [doc patch] a slight VACUUM / VACUUM FULL doc improvement proposal
In-Reply-To: <20070516161702.GN14548@nasby.net>
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