Giorgio Valoti <giorgio_v@xxxxxxx> writes: > GroupAggregate (cost=98431.58..119773.92 rows=74226 width=8) > -> Sort (cost=98431.58..99050.92 rows=247736 width=8) > Sort Key: (day_trunc(ts)) > -> Seq Scan on blackbox (cost=0.00..72848.36 rows=247736 width=8) > GroupAggregate (cost=0.00..19109.66 rows=74226 width=8) > -> Index Scan using test_2_idx on blackbox (cost=0.00..16943.16 rows=247736 width=8) These numbers seem pretty bogus: there is hardly any scenario in which a full-table indexscan should be costed as significantly cheaper than a seqscan. Have you put in silly values for random_page_cost? If you haven't mucked with the cost parameters, the only way I can think of to get this result is to have an enormously bloated table that's mostly empty. Maybe you need to review your vacuuming procedures. regards, tom lane
