2010/1/5 Roman Neuhauser <neuhauser+pgsql-general#postgresql.org@sigpipe.cz>:
> # Jayadevan.Maymala@ibsplc.com / 2010-01-04 10:03:29 +0530:
>> This seems to work..
>> UPDATE x set i=i+1
>> from (select i as m from x order by m desc) y where x.i = y.m
>> Jayadevan
>
> Thanks, that nicely achieves the illusion of atomic immediate checking.
>
> --
> Roman Neuhauser
That is not guaranteed to work. Depending on how the optimiser does
the join, the reverse ordering may not be preserved in the update. Try
it for larger tables (for me it fails at 100000 rows).
Regards,
Dean