From: Tom Lane <tgl@sss.pgh.pa.us>
To: Daryl Herzmann <akrherz@iastate.edu>
Cc: pgsql-performance@postgresql.org
Subject: Re: Missing the point of autovacuum
Date: Sat, 06 Jan 2007 14:46:40 -0500
Message-ID: <17824.1168112800@sss.pgh.pa.us> (raw)
In-Reply-To: <Pine.LNX.4.61.0701061247440.5569@ics128-198.icsincorporated.com>
References: <Pine.LNX.4.61.0701061247440.5569@ics128-198.icsincorporated.com>
Daryl Herzmann <akrherz@iastate.edu> writes:
> As the months have gone by, I notice many of my tables having *lots* of
> unused item pointers. For example,
> There were 31046438 unused item pointers.
> Total free space (including removable row versions) is 4894537260 bytes.
> 580240 pages are or will become empty, including 7 at the end of the
> table.
> 623736 pages containing 4893544876 free bytes are potential move
> destinations.
This definitely looks like autovac is not getting the job done for you.
The default autovac settings in 8.1 are very un-aggressive and many
people find that they need to change the settings to make autovac vacuum
more often. Combining autovac with the traditional approach of a cron
job isn't a bad idea, either, if you have known slow times of day ---
autovac doesn't currently have any concept of a maintenance window,
so if you'd rather your vacuuming mostly happened at 2AM, you still need
a cron job for that.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, akrherz@iastate.edu
Subject: Re: Missing the point of autovacuum
In-Reply-To: <17824.1168112800@sss.pgh.pa.us>
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