On Thu, Feb 4, 2010 at 3:24 AM, Glenn Maynard <glenn@xxxxxxxx> wrote: > On Wed, Feb 3, 2010 at 10:05 PM, Robert Haas <robertmhaas@xxxxxxxxx> wrote: >> Rewriting it as a join will likely be faster still: >> >> SELECT r.id FROM stomp_steps s, stomp_round r WHERE (s.id IS NULL OR >> r.steps_id = s.id) AND ($1 IS NULL OR r.user_card_id = $1) ORDER BY >> r.score DESC LIMIT $2 > > That's not the same; this SELECT will only find the N highest scores, > since the LIMIT applies to the whole results. Mine finds the highest > scores for each stage (steps), since the scope of the LIMIT is each > call of the function (eg. "find the top score for each stage" as > opposed to "find the top five scores for each stage"). > > That's the only reason I used a function at all to begin with--I know > no way to do this with a plain SELECT. Oh, I get it. Yeah, I don't think you can do that without LATERAL(), which we don't have, unless the window-function thing works... ...Robert -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
