Message-ID: <3DDC110B.3030502@intransa.com>
Date: Wed, 20 Nov 2002 14:47:39 -0800
From: Medi Montaseri <medi.montaseri@intransa.com>
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To: Neil Conway <neilc@samurai.com>
Cc: Francisco Reyes <lists@natserv.com>,
	pgsql General List <pgsql-general@postgresql.org>
Subject: Re: Closing inactive connections OR user connections limits
References: <20021120135345.S30106-100000@zoraida.natserv.net>
	<3DDBDBE5.6000505@intransa.com>
	<87wun83p0k.fsf@mailbox.samurai.com>
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Its my understanding that vacuum actually removes tuples that have been 
updated or deleted.
Sort of like emptying your trash .... whence a tuple has been removed, 
no rollback can set the
state back. If you have logically removed a tuple (not vacuumed yet), 
then one can rollback,
but if you vacuum then you can not rollback.

Now suppose transaction A decides to delete some tuples, a vacuum job 
comes along and
deletes things (in parallel), trans A decides to rollback....engines who 
support parallel
vacuum-ing and transactions such as PG 7.2 better have a way of 
protecting themselves
against this....

Correct me if ...

Neil Conway wrote:

>Medi Montaseri <medi.montaseri@intransa.com> writes:
>  
>
>>I think from the data integrity point of view, vacuum is more
>>important than vacuum full.
>>    
>>
>
>Why would VACUUM have any effect on data integrity, either positive or
>negative?
>
>Cheers,
>
>Neil
>
>  
>