Re: autovacuum not freeing up unused space on 8.3.0

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Stuart Brooks <stuartb(at)cat(dot)co(dot)za>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: autovacuum not freeing up unused space on 8.3.0
Date: 2008-02-26 15:50:44
Message-ID: 3032.1204041044@sss.pgh.pa.us
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Stuart Brooks <stuartb(at)cat(dot)co(dot)za> writes:
> Process 2:
> - running ANALYZE VERBOSE and pg_total_relation_size every second

> The result is that autovacuum appears to be canceled.

Yes, that will pretty much guarantee that an autovacuum is never able to
complete...

> What concerns me is that once the size has grown, even a VACUUM FULL
> doesn't recover the space. Regular external VACUUMs keep the table at
> around 10MB but if I use autovacuum and it grows to 40MB, a VACUUM FULL
> will only get it down to 35MB. Is it possible that a canceled autovacuum
> could result in permanently lost space?

Are you measuring index as well as table size? VACUUM FULL is no good
at compacting indexes.

regards, tom lane

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