Analysis:
========
While debugging bitmap heap scan (BitmapHeapNext function) found that first we perform the underlying index scan and then iterate over bitmap. Now while iterating, we execute ExecQual only if tbmres->recheck is true. And for the query tbmres->recheck is false.
But from the query it seems that we should execute ExecQual as we having "bitmpaqual" on the BitmapHeap node (Not quite sure). And when I manually did recheck = ture, query working fine and as expected.
Regards.
Rushabh
www.EnterpriseDB.comOn Wed, Nov 19, 2008 at 4:26 PM, Rushabh Lathia
<rushabh.lathia@gmail.com> wrote:
Simple select give wrong result when it uses the Bitmap Heap Scan path.
postgres=# CREATE OR REPLACE FUNCTION my_exec_im_test_func(i integer) RETURNS integer AS $$
BEGIN
RETURN i + 1;
END;
$$ LANGUAGE plpgsql;
CREATE FUNCTION
postgres=# set enable_seqscan=off;
SET
postgres=# set enable_indexscan=off;
SET
postgres=# select proname from pg_proc where proname like 'my_pro1';
proname
----------------------
my_exec_im_test_proc
(1 row)
postgres=# explain select proname from pg_proc where proname like 'my_pro1';
QUERY PLAN
--------------------------------------------------------------------------------
-------------
Bitmap Heap Scan on pg_proc (cost=4.26..8.27 rows=1 width=64)
Recheck Cond: (proname ~~ 'my_pro1'::text)
-> Bitmap Index Scan on pg_proc_proname_args_nsp_index (cost=0.00..4.26 row
s=1 width=0)
Index Cond: ((proname >= 'my'::name) AND (proname < 'mz'::name))
(4 rows)
--
Rushabh Lathia
www.EnterpriseDB.com
--
Rushabh Lathia
