Re: Why is postgres autovacuuming a table that is never updated?

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Joseph S <jks(at)selectacast(dot)net>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Why is postgres autovacuuming a table that is never updated?
Date: 2008-04-29 19:10:58
Message-ID: 20080429191058.GG5652@alvh.no-ip.org
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Joseph S wrote:
> I'm running 8.2.6. I have a log table that is always INSERTed to, and
> no updates or deletes are ever run on. For some reason the autovacuum
> decided it needed to vacuum this table, and it is slowing down my
> production server.

Perhaps it's because the table is close to Xid wraparound. Please see

select age(relfrozenxid) from pg_class where oid = 'your-table'::regclass;

If the age exceeds max freeze age, then this is the cause. (The
freeze max age can come from the freeze_max_age param, or
autovacuum_freeze_max_age, or pg_autovacuum.freeze_max_age).

Hmm, maybe it's called max_freeze_age, I don't recall offhand.

Beware of the pg_autovacuum column being zero.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

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