On Mon, Apr 18, 2005 at 10:44:43AM -0500, Dave Held wrote: > Since you are fetching the entire table, you are touching all the rows. > If the query were to fetch the rows in index order, it would be seeking > all over the table's tracks. By fetching in sequence order, it has a > much better chance of fetching rows in a way that minimizes head seeks. > Since disk I/O is generally 10-100x slower than RAM, the in-memory sort > can be surprisingly slow and still beat indexed disk access. Of course, > this is only true if the table can fit and be sorted entirely in memory > (which, with 1500 rows, probably can).
Actually, the planner (at least in 7.4) isn't smart enough to consider if the sort would fit in memory or not. I'm running a test right now to see if it's actually faster to use an index in this case. -- Jim C. Nasby, Database Consultant [EMAIL PROTECTED] Give your computer some brain candy! www.distributed.net Team #1828 Windows: "Where do you want to go today?" Linux: "Where do you want to go tomorrow?" FreeBSD: "Are you guys coming, or what?" ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly