tti=# explain select call_type, flow, SUM(minutes) AS total_minutes FROM pstn_cdr WHERE calldate >= '2006-07-01 00:00:00' AND calldate < '2006-08-01 00:00:00' GROUP BY call_type, flow;
                                                                            QUERY PLAN 
------------------------------------------------------------------------------------------------------------------------------------------------------------------
 HashAggregate  (cost=49500.45..49502.95 rows=200 width=25)
   ->  Bitmap Heap Scan on pstn_cdr  (cost=183.31..49352.57 rows=19718 width=25)
         Recheck Cond: ((calldate >= '2006-07-01 00:00:00'::timestamp without time zone) AND (calldate < '2006-08-01 00:00:00'::timestamp without time zone))
         ->  Bitmap Index Scan on calldate_idx  (cost=0.00..183.31 rows=19718 width=0)
               Index Cond: ((calldate >= '2006-07-01 00:00:00'::timestamp without time zone) AND (calldate < '2006-08-01 00:00:00'::timestamp without time zone))
(5 rows)