On Sat, Mar 15, 2003 at 09:23:28AM -0600, Bruno Wolff III wrote: > On Fri, Mar 14, 2003 at 14:19:46 -0600, > Taral <[EMAIL PROTECTED]> wrote: > > Same setup, different query: > > > > test=> explain select max(time) from test where id = '1'; > > NOTICE: QUERY PLAN: > > > > Aggregate (cost=5084.67..5084.67 rows=1 width=0) > > -> Index Scan using idx on test (cost=0.00..5081.33 rows=1333 width=0) > > > > Since the index is (id, time), why isn't the index being used to > > retrieve the maximum value? > > It looks like an index scan is being done. > > If the index was on (time, id) instead of (id, time), then you could get > a further speed up by rewriting the query as: > select time from test where id = '1' order by time desc limit 1;
Yes, that's exactly it. It's an index _scan_. It should simply be able to read the maximum straight from the btree. -- Taral <[EMAIL PROTECTED]> This message is digitally signed. Please PGP encrypt mail to me. "Most parents have better things to do with their time than take care of their children." -- Me
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