Date: Wed, 16 May 2007 12:38:04 -0400
From: Alvaro Herrera <alvherre@commandprompt.com>
To: Heikki Linnakangas <heikki@enterprisedb.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Chris Browne <cbbrowne@acm.org>,
	pgsql-patches@postgresql.org
Subject: Re: [DOCS] Autovacuum and XID wraparound
Message-ID: <20070516163804.GB4582@alvh.no-ip.org>
References: <20070514011740.GH14860@fetter.org>
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	<60sl9z6tln.fsf@dba2.int.libertyrms.com>
	<20070514221619.GC8916@alvh.no-ip.org>
	<857.1179184222@sss.pgh.pa.us>
	<20070515221347.GT12731@alvh.no-ip.org>
	<23362.1179292856@sss.pgh.pa.us>
	<20070516124420.GA4582@alvh.no-ip.org>
	<464B0E5A.1070807@enterprisedb.com>
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Heikki Linnakangas wrote:
> Alvaro Herrera wrote:
> >However, given that Heikki just confirmed that CLUSTER does not freeze
> >tuples, it's not really possible to do this, so I'll drop the CLUSTER
> >patch for now.
> >
> >This means that people using CLUSTER to compact tables won't have the
> >benefit of advancing relfrozenxid, so they will have to run VACUUM on
> >those tables at some point anyway, even though there will be no dead
> >tuples :-(
> 
> Now that I think this a bit more, I think CLUSTER should freeze the 
> tuples. I was worried about losing valuable debug information by doing 
> that, but thinking a bit more that's not a big concern: we wouldn't 
> freeze tuples newer than recent xmin. The update chain logic is the most 
> risky part of the code, and we wouldn't lose the xmin and xmax of tuples 
> that are part of update chains.
> 
> Patch attached. You'll need the changes to cluster.c to set the 
> relfrozenid as well.

Thanks, committed.  (I changed NULL for InvalidBuffer).

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