Yann Michel <[EMAIL PROTECTED]> writes: > On Wed, Dec 22, 2004 at 01:52:40PM -0800, Litao Wu wrote: >> Does the order of columns in the index matter since >> more than 50% customer_id = 158? >> >> I think it does not in Oracle. >> >> Will the performance be better if I change index >> xxx_idx to ("domain", customer_id, created)? > > Well, in Oracle this would of cause matter. Oracle calculates index > usage by being able to fill all index's attributes from the left to the > right. If any one attribute within is missing Oracle would not test if > it is only one attribute missing, or if all other attributes are missing > within the query's where clause.
This depends on the version of Oracle you're using. Oracle 9i introduced Index Skip Scans: http://www.oracle.com/technology//products/oracle9i/daily/apr22.html I don't know whether pg has something similar? ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org