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Re: Questions about update, delete, ctid...

From: DANTE Alexandra <Alexandra(dot)Dante(at)bull(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Martijn van Oosterhout <kleptog(at)svana(dot)org>,pgsql-general(at)postgresql(dot)org
Subject: Re: Questions about update, delete, ctid...
Date: 2006-07-31 15:00:55
Message-ID: 44CE1B27.1090705@bull.net (view raw or flat)
Thread:
Lists: pgsql-general
Hello Tom, Martijn and List,

Thank you for yours answers !
This point is now closed for me and I can go further in the mecanisms of 
VACUUM.

Regards,
Alexandra


Tom Lane wrote:

>DANTE Alexandra <Alexandra(dot)Dante(at)bull(dot)net> writes:
>  
>
>>    - during a SELECT query on a tuple just updated and commited, does 
>>the executor first detect the old tuple and then via the c_tid link go 
>>to the new version of the tuple ? or go directly to the new version ?
>>    
>>
>
>Neither.  SELECT doesn't care about update relationships, it just
>returns whatever row version is current according to its snapshot.
>It's only UPDATE/DELETE that are constrained to act on the most
>current version of each row.
>
>			regards, tom lane
>
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>


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