Skip site navigation (1) Skip section navigation (2)

Re: [doc patch] a slight VACUUM / VACUUM FULL doc improvement proposal

From: "Jim C(dot) Nasby" <decibel(at)decibel(dot)org>
To: Guillaume Cottenceau <gc(at)mnc(dot)ch>
Cc: Michael Stone <mstone+postgres(at)mathom(dot)us>,pgsql-performance(at)postgresql(dot)org
Subject: Re: [doc patch] a slight VACUUM / VACUUM FULL doc improvement proposal
Date: 2007-05-16 15:48:09
Message-ID: 20070516154809.GL14548@nasby.net (view raw or flat)
Thread:
Lists: pgsql-docspgsql-performance
On Wed, May 16, 2007 at 09:41:46AM +0200, Guillaume Cottenceau wrote:
> 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?

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.

Long term I think we should ditch 'VACUUM FULL' altogether and create a
COMPACT command (it's very easy for users to get confused between
"vacuum all the databases in the cluster" or "vacuum the entire
database" and "VACUUM FULL").
-- 
Jim Nasby                                      decibel(at)decibel(dot)org
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

In response to

Responses

pgsql-docs by date

Next:From: Michael GlaesemannDate: 2007-05-16 15:52:05
Subject: Re: [PATCHES] OS/X startup scripts
Previous:From: Andrew DunstanDate: 2007-05-16 15:22:11
Subject: Re: [PATCHES] OS/X startup scripts

pgsql-performance by date

Next:From: Jim C. NasbyDate: 2007-05-16 15:51:45
Subject: Re: Disk Fills Up and fsck "Compresses" it
Previous:From: Luke LonerganDate: 2007-05-16 15:38:36
Subject: Re: New performance documentation released

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group