On Fri, 30 May 2003, Bruno Wolff III wrote:
> Now that expressions can be used in indexes in 7.4 you can have multicolumn
> indexes that are ordered in different directions. However the planner
> doesn't seem to understand that order by -col asc is the same as order by
> col desc (for at least the normal -) so you have to be careful how you
> write queries when doing this.
I think it'd be better to make it easier to make indexes where some
columns are reversed. I'm not sure that making a reverse opclass for
btree (one that goes >, >=, =, <=, < I guess) is a complete solution
even for btree but if it is, we could provide them. I think this would
also have the advantage of not requiring wacky queries to use the index
for multicolumn lookups as well.