On 07/ago/08, at 17:50, Tom Lane wrote:
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?
No,
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.
I’ll review them.
Thank you
--
Giorgio Valoti
