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

From: "Florian G(dot) Pflug" <fgp(at)phlo(dot)org>
To: DANTE Alexandra <Alexandra(dot)Dante(at)bull(dot)net>, pgsql-general(at)postgresql(dot)org, kleptog(at)svana(dot)org
Subject: Re: Questions about update, delete, ctid...
Date: 2006-07-30 14:37:26
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-general
Martijn van Oosterhout wrote:
> On Fri, Jul 28, 2006 at 12:00:19PM +0200, DANTE Alexandra wrote:
>> - is it correct to think that the ctid of the old version of the tuple 
>> is a link to newer version ? In my example, is it correct to think that 
>> the tuple :
>> 140049    |    0 | (0,12) |          11 | IRAQ
>> has become :
>> new value |    0 | (0,26) |          11 | ITALY
> The word "become" is not really right. The old version has become
> invisible to you and the new version is visible. Some other
> transactions will see the old one, some the new one. However, there is
> a link between the old and the new version do detect conflicting
> updates.

That sounds interesting... how is that link between old and new
tuple implemented? I've been playing with the idea to implement
"update table foo where current of <cursor>", and such a link
would help tremendously. I read the code, but couldn't find any
such link - which part of the code should I read closer?

greetings, Florian Pflug

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