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Re: VACUUMs take twice as long across all nodes

From: "Jim C(dot) Nasby" <jim(at)nasby(dot)net>
To: Gavin Hamill <gdh(at)laterooms(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: VACUUMs take twice as long across all nodes
Date: 2006-10-26 19:17:29
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Thu, Oct 26, 2006 at 04:06:09PM +0100, Gavin Hamill wrote:
> On Thu, 26 Oct 2006 10:47:21 -0400
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Gavin Hamill <gdh(at)laterooms(dot)com> writes:
> > > Nodes 2 and 3 take only the tables necessary to run our search (10
> > > out of the full 130) and are much lighter (only 7GB on disk cf.
> > > 30GB for the full master) , yet the nightly VACUUM FULL has jumped
> > > from 2 hours to 4 in the space of one day!
> > 
> > I guess the most useful question to ask is "why are you doing VACUUM
> > FULL?" Plain VACUUM should be considerably faster, and for the level
> > of row turnover shown by your log, there doesn't seem to be a reason
> > to use FULL.
> I do FULL on the 'light' clients simply because 'I can'. The example
> posted was a poor choice - the other tables have a larger churn.
> Anyway, once it starts, the load balancer takes it out of rotation so
> no love is lost.
> The same behaviour is shown on the 'heavy' clients (master + 2 slaves)
> which take all tables - although I cannot afford to VACUUM FULL on
> there, the usual VACUUM ANALYZE has begun to take vastly more time
> since yesterday than in the many previous months we've been using pg.

Are you sure that there's nothing else happening on the machine that
could affect the vacuum times? Like, say a backup? Or perhaps updates
coming in from Slony that didn't used to be there?
Jim Nasby                                            jim(at)nasby(dot)net
EnterpriseDB      512.569.9461 (cell)

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