Thread: Bitmap scan when it is not needed

explain analyze select * from objects_hier where tg && array[0] and id <10000;

Bitmap Heap Scan on objects_hier  (cost=4.79..8.80 rows=1 width=337) (actual time=0.110..0.110 rows=0 loops=1)

   Recheck Cond: ((tg && '{0}'::integer[]) AND (id < 10000))

   ->  BitmapAnd  (cost=4.79..4.79 rows=1 width=0) (actual time=0.106..0.106 rows=0 loops=1)

         ->  Bitmap Index Scan on gistbla2  (cost=0.00..2.10 rows=30 width=0) (actual time=0.042..0.042 rows=0 loops=1)

               Index Cond: (tg && '{0}'::integer[])

         ->  Bitmap Index Scan on ohid  (cost=0.00..2.44 rows=1240 width=0) (actual time=0.058..0.058 rows=1255 loops=1)

               Index Cond: (id < 10000)

I see, Bitmap is going to AND my indexes.. It read one with less number of rows estimated the first (right)..

It found 0 records at gistbla2 index…

Then why is it reading ohid ? 

Maybe a quickfix is possible for cases when 0 records is found to stop reading other AND elements..