Re: 8.2 Autovacuum BUG ?

From: Pallav Kalva <pkalva(at)livedatagroup(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: 8.2 Autovacuum BUG ?
Date: 2007-08-31 16:05:36
Message-ID: 46D83C50.3040409@livedatagroup.com
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Tom Lane wrote:
> Pallav Kalva <pkalva(at)livedatagroup(dot)com> writes:
>
>> We turned on autovacuums on 8.2 and we have a database which is read
>> only , it is basically a USPS database used only for address lookups
>> (only SELECTS, no updates/deletes/inserts).
>>
>
>
>> This database has about 10gig data and yesterday autovacuum started
>> on this database and all of a sudden I see lot of archive logs generated
>> during this time, I guess it might have generated close to 3-4gig data
>> during this period.
>>
>
> 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 ?
If I am doing just SELECTS on these tables ? how can there be any
transactions ? or SELECTS considered transactions too ?

> regards, tom lane
>
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