From: Alvaro Herrera <alvherre@commandprompt.com>
To: Pallav Kalva <pkalva@livedatagroup.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: 8.2 Autovacuum BUG ?
Date: Fri, 31 Aug 2007 12:11:58 -0400
Message-ID: <20070831161158.GD8046@alvh.no-ip.org> (raw)
In-Reply-To: <46D83C50.3040409@livedatagroup.com>
References: <46D83427.60001@livedatagroup.com>
<25038.1188574775@sss.pgh.pa.us>
<46D83C50.3040409@livedatagroup.com>
Pallav Kalva wrote:
> Tom Lane wrote:
>> Probably represents freezing of old tuples, which is a WAL-logged
>> operation as of 8.2. Is it likely that the data is 200M transactions
>> old?
>>
> If nothing changed on these tables how can it freeze old tuples ?
> Does it mean that once it reaches 200M transactions it will do the same
> thing all over again ?
No -- once tuples are frozen, they don't need freezing again (unless
they are modified by UPDATE or DELETE).
> If I am doing just SELECTS on these tables ? how can there be any
> transactions ? or SELECTS considered transactions too ?
Selects are transactions too. They just don't modify data.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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To: pgsql-performance@postgresql.org
Cc: alvherre@commandprompt.com, pkalva@livedatagroup.com, tgl@sss.pgh.pa.us
Subject: Re: 8.2 Autovacuum BUG ?
In-Reply-To: <20070831161158.GD8046@alvh.no-ip.org>
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