Subject RE: [IB-Architect] order by not using index
Author Leyne, Sean

The reason that the index is not used is that generally speaking it is
more efficient to navigate a table in the natural order and then sort
the results, then to use the index and then hop back-and-forth through
the table. The natural order approach involves less disk I/O and
therefore is a faster approach.

Accordingly, the optimizer tends to use indexes for criteria purposes
not order.