From: Tom Lane <tgl@sss.pgh.pa.us>
To: Dave North <DNorth@signiant.com>
Cc: Richard Huxton <dev@archonet.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Database size Vs performance degradation
Date: Wed, 30 Jul 2008 11:05:16 -0400
Message-ID: <25537.1217430316@sss.pgh.pa.us> (raw)
In-Reply-To: <35FABCF85D99464FB00BC5123DC2A70A051D0FEC@s228130hz1ew09.apptix-01.savvis.net>
References: <35FABCF85D99464FB00BC5123DC2A70A051D0FB8@s228130hz1ew09.apptix-01.savvis.net>
<48905E59.9040007@archonet.com>
<35FABCF85D99464FB00BC5123DC2A70A051D0FEC@s228130hz1ew09.apptix-01.savvis.net>
"Dave North" <DNorth@signiant.com> writes:
> From: Richard Huxton [mailto:dev@archonet.com]
>> Well, that's pretty much the definition of bloat. Are you sure you're
>> vacuuming enough?
> DN: Well, the auto-vac is kicking off pretty darn frequently...around
> once every 2 minutes. However, you just made me think of the obvious -
> is it actually doing anything?! The app is pretty darn write intensive
> so I wonder if it's actually able to vacuum the tables?
IIRC, the default autovac parameters in 8.1 were pretty darn
unaggressive. You should also check for long-running transactions
that might be preventing vacuum from removing recently-dead rows.
One of the reasons for updating off 8.1 is that finding out what autovac
is really doing is hard :-(. I think it does log, but at level DEBUG2
or so, which means that the only way to find out is to accept a huge
amount of useless chatter in the postmaster log. Newer releases have
a saner logging scheme.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, DNorth@signiant.com, dev@archonet.com
Subject: Re: Database size Vs performance degradation
In-Reply-To: <25537.1217430316@sss.pgh.pa.us>
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