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Re: Stupid question on Read Committed Isolation Level - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Stupid question on Read Committed Isolation Level
Date
Msg-id 25090.1075399619@sss.pgh.pa.us
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In response to Stupid question on Read Committed Isolation Level  ("Marc G. Fournier" <scrappy@hub.org>)
Responses Re: Stupid question on Read Committed Isolation Level  ("Marc G. Fournier" <scrappy@postgresql.org>)
Re: Stupid question on Read Committed Isolation Level  (Chris Bowlby <chris@pgsql.com>)
Re: Stupid question on Read Committed Isolation Level  (Greg Stark <gsstark@mit.edu>)
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"Marc G. Fournier" <scrappy@hub.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.
        regards, tom lane

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