From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | "Dave North" <DNorth(at)signiant(dot)com> |
Cc: | "Richard Huxton" <dev(at)archonet(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Database size Vs performance degradation |
Date: | 2008-07-30 15:05:16 |
Message-ID: | 25537.1217430316@sss.pgh.pa.us |
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Lists: | pgsql-performance |
"Dave North" <DNorth(at)signiant(dot)com> writes:
> From: Richard Huxton [mailto:dev(at)archonet(dot)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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