Thanks for that insight Ivan.

I'm confident FB community will sooner than later improve the
optimizer to be smarter and/or use bi-directional indexes. Real world
scenarios can (and often do) make use of this kind of stuff.

--- In ib-support@y..., "Ivan Prenosil" <prenosil@m...> wrote:
> > Anyways, is it possible to have both, an ascending and a
descending
> > index on the same column? Will disk storage for these indexes
> > duplicate?
>
> Just to sum up:
> - ASCending index can be used to find MIN(), or to ORDER BY (ASC)
> - DESCending index can be used to find MAX(), or to ORDER BY DESC
> - WHERE clause can use either of these indexes, but if you have two
similar indexes
> that differ just by ASC/DESC direction, optimizer sometimes
incorrectly use both.
>
> Ivan
> http://www.volny.cz/iprenosil/interbase