Re: Tracking row updates - race condition - Mailing list pgsql-general

From Harald Fuchs
Subject Re: Tracking row updates - race condition
Date
Msg-id pur7hyr8zh.fsf@srv.protecting.net
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In response to Tracking row updates - race condition  (Alex Adriaanse <alex@alexandcarmen.com>)
Responses Re: Tracking row updates - race condition  (Alex Adriaanse <alex@alexandcarmen.com>)
List pgsql-general
In article <4248E1AE.8090404@alexandcarmen.com>,
Alex Adriaanse <alex@alexandcarmen.com> writes:

> Thanks for the input everyone.  I think Harald's approach will work
> well...

I'm not so sure anymore :-(

Consider something like that:

UPDATE tbl SET col1 = 1 WHERE col2 = 1;
UPDATE tbl SET col1 = 2 WHERE col2 = 1;

with not much time inbetween.  By using NULL temporarily, you destroy
the ordering.  The client won't miss an UPDATE, but it might execute
the second one before the first.  Neither my nor your idea appear to
take care of that.

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