> [!NOTE] Bitmap And / Bitmap Or > <table> > <tr> > <td width="25%"><img src="assets/ex_bitmapandbitmapor.png"></td> > <td>Combines multiple TID bitmaps using bitwise logic.</td> > </tr> > </table> > > ```sql > -- Combining results from two separate indexes > SET enable_seqscan = off; > > EXPLAIN (ANALYZE, COSTS, BUFFERS, VERBOSE) > SELECT * FROM animals > WHERE species_id = 1 OR species_id = 5; > ``` > >  > > ```text > Bitmap Heap Scan on public.animals (cost=56.37..190.37 rows=3600 width=27) (actual time=0.092..0.508 rows=4000 loops=1) > Output: id, name, species_id, created_at > Recheck Cond: ((animals.species_id = 1) OR (animals.species_id = 5)) > Heap Blocks: exact=74 > Buffers: shared hit=80 > -> BitmapOr (cost=56.37..56.37 rows=4000 width=0) (actual time=0.078..0.078 rows=0 loops=1) > Buffers: shared hit=6 > -> Bitmap Index Scan on idx_animals_species_id (cost=0.00..27.29 rows=2000 width=0) (actual time=0.044..0.044 rows=2000 loops=1) > Index Cond: (animals.species_id = 1) > Buffers: shared hit=3 > -> Bitmap Index Scan on idx_animals_species_id (cost=0.00..27.29 rows=2000 width=0) (actual time=0.034..0.034 rows=2000 loops=1) > Index Cond: (animals.species_id = 5) > Buffers: shared hit=3 > Planning: > Buffers: shared hit=84 > Planning Time: 0.364 ms > Execution Time: 0.655 ms > ``` > >  > > <table> > <tr> > <td rowspan="2" width="25%"><img src="assets/ex_bmp_and.svg" style="width: 48%;"><img src="assets/ex_bmp_or.svg" style="width: 48%;"></td> > <td><b>Performance</b></td><td>Combines index-produced TID bitmaps before visiting the heap, avoiding unnecessary page fetches.</td> > </tr> > <tr><td><b>Cost</b></td><td><code>input bitmap costs + bitmap combination + matching heap pages</code></td></tr> > </table>