Thread

1. EXPLAIN ANALYZE for bitmapAnd and bitmapOr scans always reports rows = 0

   Joseph Shraibman <jks@selectacast.net> — 2007-07-31T22:26:46Z

    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)
   
   

2. Re: EXPLAIN ANALYZE for bitmapAnd and bitmapOr scans always reports rows = 0

   Heikki Linnakangas <heikki@enterprisedb.com> — 2007-08-01T19:02:45Z

   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