Simon Riggs <simon@2ndQuadrant.com> writes:
> Both plans for this query show an IndexScan on a two column-index, with
> an Index Condition of equality on the leading column. The ORDER BY
> specifies a sort by the second index column, so the top-level Sort is
> superfluous in this case.
> My understanding is that we don't currently eliminate superfluous
> additional sorts of this kind.
Nonsense. The planner might think some other plan is cheaper, but
it definitely knows how to do this, and has since at least 8.1.
regards, tom lane