On Mon, Jun 14, 2010 at 11:58 AM, Dave Crooke <dcro...@gmail.com> wrote: > If you're doing straight SQL bulk updates, then as someone suggested, you > could use an ORDER BY on a subquery, but I don't know if that is a guarantee, > if you're not actually displaying the results then the DB may be technically > allowed to optimize it out from underneath you. The only way to be sure is a > cursor / procedure.
'order by' should be safe if you use SELECT...FOR UPDATE. update doesn't have an order by clause. Using cursor/procedure vs a query is not the material point; you have to make sure locks are acquired in a regular way. update foo set x=x where id in (select * from bar order by x) does look dangerous. I think: update foo set x=x where id in (select * from bar order by x for update) should be ok. I don't usually do it that way. merlin -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
