Обсуждение: EXPLAIN ANALYZE for bitmapAnd and bitmapOr scans always reports rows = 0
From this snipped you can see that the Bitmap Heap scan returns 123 rows, but the BitmapAnd under it returns 0. I would find it useful to determine how many rows were thrown out by the recheck. -> Bitmap Heap Scan on d (cost=4959.18..16848.23 rows=754 width=10) (actual time=344.126..1534.198 rows=123 loops=1) Recheck Cond: ((s = $0) AND (sdate >= '2007-06-30'::date) AND (sdate <= '2007-07-30'::date)) Filter: (snipped filter conditions here) -> BitmapAnd (cost=4959.18..4959.18 rows=3218 width=0) (actual time=337.002..337.002 rows=0 loops=1) -> Bitmap Index Scan on d_idx1 (cost=0.00..1035.58 rows=54796 width=0) (actual time=96.478..96.478 rows=30338 loops=1) Index Cond: (s = $0) -> Bitmap Index Scan on d_idx2 (cost=0.00..3922.98 rows=183437 width=0) (actual time=235.680..235.680 rows=181322 loops=1) Index Cond: ((sdate >= '2007-06-30'::date) AND (sdate <= '2007-07-30'::date)) This was on: PostgreSQL 8.2.4 on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 3.4.6 20060404 (Red Hat 3.4.6-3)
Re: EXPLAIN ANALYZE for bitmapAnd and bitmapOr scans always reports rows = 0
От
Heikki Linnakangas
Дата:
Joseph S wrote: > From this snipped you can see that the Bitmap Heap scan returns 123 > rows, but the BitmapAnd under it returns 0. I would find it useful to > determine how many rows were thrown out by the recheck. Yeah, it would be nice. Unfortunately there's some problems with that, see previous discussion on that: http://archives.postgresql.org/pgsql-bugs/2007-04/msg00029.php -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com