From: | "Marc G(dot) Fournier" <scrappy(at)postgresql(dot)org> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Stupid question on Read Committed Isolation Level |
Date: | 2004-01-29 18:09:07 |
Message-ID: | 20040129140817.Q6922@ganymede.hub.org |
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Lists: | pgsql-hackers |
On Thu, 29 Jan 2004, Tom Lane wrote:
> "Marc G. Fournier" <scrappy(at)hub(dot)org> writes:
> > What happens if I abort on the first transaction? If I'm reading this
> > right, if Trans2 does the exact same as above, and COMMITs before Trans1
> > Aborts, the value of balance becomes +200 (Trans2 + Trans1) ... but what
> > happens when Trans1 ABORTS? Trans2 believes its COMMIT worked, but
> > ABORTng Trans1 will rollback to the original value, no?
>
> If trans2 is the second to get to the row, it will *wait* until trans1
> either commits or aborts, and then use the new or old version of the row
> accordingly. The scenario you are thinking of can't happen.
Thank you, that answers it ... so, simplistically, since they are both
hitting the same row, there is a pseudo-commit lock on that row by the
first transaction ...
----
Marc G. Fournier Hub.Org Networking Services (http://www.hub.org)
Email: scrappy(at)hub(dot)org Yahoo!: yscrappy ICQ: 7615664
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