Simon Riggs <simon@2ndquadrant.com> writes:
> Perhaps we should call it 'Ordered Scan' so that it is completely
> different from 'Index Scan'?
It's not an either/or proposition; the planner could be using the index
for both selectivity and ordering. This discussion is also overlooking
the possibility that a partial index is being used for its predicate
(again, possibly in combination with explicit index quals and/or
interest in the sort order).
regards, tom lane