Re: Speeding up SELECT MAX(),... GROUP BY ... ?

Chris,

> EXPLAIN 
> select max(timepoint),lid,mid,sid from onfvalue 
> where  timepoint <= '2002-05-01 08:00:00'  and  sid in (1,3,5,7)  group by 
sid,lid,mid; 

Having indexes on all four columns will help.  Beyond that, there's not a lot 
you can do; aggregate queries are slow.  Rely on raw hardware power 
(multi-channel SCSI, fast processor, lots of RAM and a very high sort_mem 
setting).

BTW, if those four columns are the only data in the table, a Seq Scan is 
actually the fastest method.   

-- 
-Josh Berkus

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