Shawn,
> I can also change the schema to a certain extent, so would it be worthwhile
> to put indices on the queried tables (or refactor them) hoping the distinct
> does an index scan instead of sort... would the query planner take
> advantage of that?
Use the GROUP BY, with an index on the grouped columns and lots of work_mem
(sort_mem in 7.4). This will give the planner the option of a hashaggregate
which could be significantly faster than the other methods.
--
Josh Berkus
Aglio Database Solutions
San Francisco