On Wed, Mar 29, 2006 at 12:52:31PM +0200, Theo Kramer wrote: > On Fri, 2006-03-24 at 12:21, Jim C. Nasby wrote: > > On Thu, Mar 23, 2006 at 01:09:49PM +0200, Theo Kramer wrote: > > > ii If no to i, is it feasible to extend PostgreSQL to allow traversing > > > an index in column descending and column ascending order - assuming > > > an order by on more than one column with column order not > > > in the same direction and indexes existing? ... if that makes sense. > > > > Yes. > > > > stats=# explain select * from email_contrib order by project_id desc, id desc, date desc limit 10; > > QUERY PLAN > > ------------------------------------------------------------------------------------------------------------------------ > > Limit (cost=0.00..31.76 rows=10 width=24) > > -> Index Scan Backward using email_contrib_pkey on email_contrib (cost=0.00..427716532.18 rows=134656656 width=24) > > (2 rows) > > Not quite what I mean - redo the above as follows and then see what > explain returns > > explain select * from email_contrib order by project_id, id, date desc > limit 10; Ahh. There's a hack to do that by defining a new opclass that reverses < and >, and then doing ORDER BY project_id, id, date USING new_opclass. I think there's a TODO about this, but I'm not sure... -- Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
