set effective_io_concurrency=0; set enable_indexscan=off; set enable_seqscan=off; explain (analyze, buffers)  select * from test where id between 64 and 100000 and val != '';
                                                        QUERY PLAN                                                        
--------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=92.009..379.511 rows=99937 loops=1)
   Recheck Cond: ((id >= 64) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1539
   Buffers: shared read=1814
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=72.641..72.641 rows=99937 loops=1)
         Index Cond: ((id >= 64) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 237.338 ms
 Execution time: 385.628 ms
(10 rows)

set effective_io_concurrency=1; set enable_indexscan=off; set enable_seqscan=off; explain (analyze, buffers)  select * from test where id between 64 and 100000 and val != '';
                                                        QUERY PLAN                                                        
--------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=93.715..705.176 rows=99937 loops=1)
   Recheck Cond: ((id >= 64) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1539
   Buffers: shared read=1814
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=89.992..89.992 rows=99937 loops=1)
         Index Cond: ((id >= 64) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 99.287 ms
 Execution time: 712.261 ms
(10 rows)

set effective_io_concurrency=0; set enable_indexscan=off; set enable_seqscan=off; explain (analyze, buffers)  select * from test where id between 64 and 100000 and val != '';
                                                          QUERY PLAN                                                          
------------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=1174.024..1604.133 rows=99937 loops=1)
   Recheck Cond: ((id >= 64) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1539
   Buffers: shared read=1814
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=1170.372..1170.372 rows=99937 loops=1)
         Index Cond: ((id >= 64) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 59.853 ms
 Execution time: 1610.618 ms
(10 rows)

set effective_io_concurrency=1; set enable_indexscan=off; set enable_seqscan=off; explain (analyze, buffers)  select * from test where id between 64 and 100000 and val != '';
                                                        QUERY PLAN                                                        
--------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=61.335..431.531 rows=99937 loops=1)
   Recheck Cond: ((id >= 64) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1539
   Buffers: shared read=1814
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=59.535..59.535 rows=99937 loops=1)
         Index Cond: ((id >= 64) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 107.171 ms
 Execution time: 438.211 ms
(10 rows)

set effective_io_concurrency=0; set enable_indexscan=off; set enable_seqscan=off; explain (analyze, buffers)  select * from test where id between 64 and 100000 and val != '';
                                                        QUERY PLAN                                                        
--------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=94.362..387.319 rows=99937 loops=1)
   Recheck Cond: ((id >= 64) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1539
   Buffers: shared read=1814
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=92.564..92.564 rows=99937 loops=1)
         Index Cond: ((id >= 64) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 94.057 ms
 Execution time: 393.341 ms
(10 rows)

set effective_io_concurrency=1; set enable_indexscan=off; set enable_seqscan=off; explain (analyze, buffers)  select * from test where id between 64 and 100000 and val != '';
                                                        QUERY PLAN                                                        
--------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=85.352..738.518 rows=99937 loops=1)
   Recheck Cond: ((id >= 64) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1539
   Buffers: shared read=1814
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=81.739..81.739 rows=99937 loops=1)
         Index Cond: ((id >= 64) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 94.554 ms
 Execution time: 744.768 ms
(10 rows)

