DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta;
	h=received:message-id:date:from:user-agent:mime-version:to:cc:subject:references:in-reply-to:content-type:sender;
	b=ZIxTa0X2LLumUgN1jiHHVNXfz6+WPSbpH/lKzfyoG6m6b6NSNypZiRJfbzY7vLyiG72Erm41nHTOOsKpLHxYVmJvn389s8UIyleo7jLlYMJ1P/H6+2/kVHOgWmVVkWLtc1Ie9WitMkeHbqHYrSB9JImFA2Z6tMHjP7nRYqW77Ng=
Message-ID: <464B0E5A.1070807@enterprisedb.com>
Date: Wed, 16 May 2007 14:59:54 +0100
From: Heikki Linnakangas <heikki@enterprisedb.com>
User-Agent: Icedove 1.5.0.10 (X11/20070329)
MIME-Version: 1.0
To: Alvaro Herrera <alvherre@commandprompt.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
References: <20070514011740.GH14860@fetter.org>
	<23394.1179108400@sss.pgh.pa.us> <1179117269.6047.3.camel@goldbach>
	<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>
In-Reply-To: <20070516124420.GA4582@alvh.no-ip.org>
Content-Type: multipart/mixed; boundary="------------070408090401080201050605"

This is a multi-part message in MIME format.
--------------070408090401080201050605
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

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.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

--------------070408090401080201050605
Content-Type: text/x-diff;
 name="cluster-freeze.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="cluster-freeze.patch"

Index: src/backend/access/heap/rewriteheap.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/access/heap/rewriteheap.c,v
retrieving revision 1.3
diff -c -r1.3 rewriteheap.c
*** src/backend/access/heap/rewriteheap.c	17 Apr 2007 21:29:31 -0000	1.3
--- src/backend/access/heap/rewriteheap.c	16 May 2007 13:42:23 -0000
***************
*** 538,543 ****
--- 538,545 ----
  	OffsetNumber	newoff;
  	HeapTuple		heaptup;
  
+ 	heap_freeze_tuple(tup->t_data, state->rs_oldest_xmin, NULL);
+ 
  	/*
  	 * If the new tuple is too big for storage or contains already toasted
  	 * out-of-line attributes from some other relation, invoke the toaster.

--------------070408090401080201050605--