Pierre-Frédéric Caillaud wrote:
>       The planner is smarter with GROUP BY than with DISTINCT, so you can
> rewrite your query as the following, whihc will probaly use a
> HashAggregate, and be a lot faster :
> 
>       SELECT service_id FROM five_min_stats_200408 GROUP BY service_id;

Pierre-Frédéric, thanks!  Vast improvement - this is definitely acceptable.  It 
did indeed use a seq scan followed by a hash aggregate.

 Total runtime: 76295.775 ms


>> estat=> explain analyze select distinct(service_id) from
>> five_min_stats_200408; QUERY PLAN
>> ------------------------------------------------------------------------
>> ------------------------------------------------------------------------
>> 
>> Time: 1284213.359 ms



-- 
Guy Rouillier


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