Re: Tracking row updates - race condition

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.