From: Tom Lane <tgl@sss.pgh.pa.us>
To: ITAGAKI Takahiro <itagaki.takahiro@oss.ntt.co.jp>
Cc: pgsql-hackers@postgresql.org
Cc: pgsql-patches@postgresql.org
Subject: Re: Aggressive freezing in lazy-vacuum
Date: Mon, 05 Mar 2007 11:02:31 -0500
Message-ID: <18982.1173110551@sss.pgh.pa.us> (raw)
In-Reply-To: <20070305182401.C4BC.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
References: <20070227141958.638D.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
<20070227170613.GK29041@nasby.net>
<20070305182401.C4BC.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
ITAGAKI Takahiro <itagaki.takahiro@oss.ntt.co.jp> writes:
> This is a stand-alone patch for aggressive freezing. I'll propose
> to use OldestXmin instead of FreezeLimit as the freeze threshold
> in the circumstances below:
I think it's a really bad idea to freeze that aggressively under any
circumstances except being told to (ie, VACUUM FREEZE). When you
freeze, you lose history information that might be needed later --- for
forensic purposes if nothing else. You need to show a fairly amazing
performance gain to justify that, and I don't think you can.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, itagaki.takahiro@oss.ntt.co.jp, pgsql-hackers@postgresql.org, pgsql-patches@postgresql.org
Subject: Re: Aggressive freezing in lazy-vacuum
In-Reply-To: <18982.1173110551@sss.pgh.pa.us>
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