Re: Why date index is not used

On Thu, Jun 08, 2006 at 03:20:55PM -0400, Tom Lane wrote:
> "Andrus"  writes:
> > Why Postgres 8.1 does not use makse_kuupaev_idx index in the following query 
> > ?
> 
> Because it doesn't help --- the system still has to do the sort.
> You'd need a two-column index on both of the ORDER BY columns to avoid
> sorting.

And even then you better have a pretty high correlation on the first
column, otherwise you'll still get a seqscan.
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461