From: Tom Lane <tgl@sss.pgh.pa.us>
To: ITAGAKI Takahiro <itagaki.takahiro@oss.ntt.co.jp>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Aggressive freezing in lazy-vacuum
Date: Tue, 06 Mar 2007 10:02:34 -0500
Message-ID: <4399.1173193354@sss.pgh.pa.us> (raw)
In-Reply-To: <20070306181253.64A9.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
References: <20070305182401.C4BC.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
<18982.1173110551@sss.pgh.pa.us>
<20070306181253.64A9.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
ITAGAKI Takahiro <itagaki.takahiro@oss.ntt.co.jp> writes:
> Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> 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.
> I don't think we can supply such a historical database functionality here,
> because we can guarantee it just only for INSERTed tuples even if we pay
> attention. We've already enabled autovacuum as default, so that we cannot
> predict when the next vacuum starts and recently UPDATEd and DELETEd tuples
> are removed at random times.
I said nothing about expired tuples. The point of not freezing is to
preserve information about the insertion time of live tuples. And your
test case is unconvincing, because no sane DBA would run with such a
small value of vacuum_freeze_min_age.
regards, tom lane
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, itagaki.takahiro@oss.ntt.co.jp, pgsql-hackers@postgresql.org
Subject: Re: Aggressive freezing in lazy-vacuum
In-Reply-To: <4399.1173193354@sss.pgh.pa.us>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox