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Re: AutoVacuum Behaviour Question

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Bruce McAlister <bruce(dot)mcalister(at)blueface(dot)ie>
Cc: Martijn van Oosterhout <kleptog(at)svana(dot)org>, pgsql-general(at)postgresql(dot)org
Subject: Re: AutoVacuum Behaviour Question
Date: 2007-06-28 14:00:40
Message-ID: 20070628140040.GB5300@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers
Bruce McAlister wrote:
> Martijn van Oosterhout wrote:
> > All the values here look OK, except one:
> > 
> > On Thu, Jun 28, 2007 at 07:50:36AM +0100, Bruce McAlister wrote:
> >> blueface-crm=# select oid, relfrozenxid from pg_class where relkind in
> >> ('r', 't');
> >>    oid   | relfrozenxid
> >> ---------+--------------
> >>  2570051 |   2947120794
> > 
> > Whatever this table is, the freeze XID isn't getting updated for some
> > reason...

Doh.

> This looks like a temporary relation,
> 
> temp4295                   |   2947120794
> 
> Is there a way we can manually force these to update?

No.  Only the session that created the temp table can vacuum it.
Autovacuum skips temp tables.  I guess the only thing you can do here is
close that session.

I'm thinking that maybe should make vac_update_datfrozenxid ignore temp
tables.  But this doesn't really work, because if we were to truncate
pg_clog there would be tuples on the temp table marked with XIDs that
are nowhere to be found.  Maybe we could make some noise about it
though.

This is a problem only in recent releases (8.2) because we started
allowing the max freeze age be configurable.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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