"Travis Whitton" <tinymountain@gmail.com> writes:
> One last question, using the "weather report" example, is it going to
> improve performance for the DISTINCT ON query to add an index to the
> location and time columns?
A two-column index matching the ORDER BY that you use might help,
or then again might not --- for full-table scans it's often faster
to sort than to try to use an index.
regards, tom lane