On 07/ago/08, at 10:35, Richard Huxton wrote:
Giorgio Valoti wrote:
Hi, I have a timestamptz field that I want to use with a query, but
I don’t need the full timestamp resolution, so I’ve created a
day_trunc(timestamptz) immutable function which I’ll use with the
query and with a new index:
logs=> create index test_idx on blackbox (day_trunc(ts));
However, the query plan doesn’t use the index:
Does it use it ever? e.g. with
SELECT * FROM blackbox WHERE day_trunk(ts) = '...'
It’s used:
logs=> explain select * from blackbox where day_trunc(ts) =
day_trunc(now());
QUERY PLAN
---------------------------------------------------------------------------
Bitmap Heap Scan on blackbox (cost=22.38..3998.43 rows=1239
width=264)
Recheck Cond: (day_trunc(ts) = day_trunc(now()))
-> Bitmap Index Scan on date_idx (cost=0.00..22.07 rows=1239
width=0)
Index Cond: (day_trunc(ts) = day_trunc(now()))
--
Giorgio Valoti
