set effective_io_concurrency=0; set enable_indexscan=off; set enable_seqscan=off; explain (analyze, buffers)  select * from test where id between 66 and 100000 and val != '';
                                                         QUERY PLAN                                                         
----------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=219.025..657.884 rows=99935 loops=1)
   Recheck Cond: ((id >= 66) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1538
   Buffers: shared read=1813
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=218.350..218.350 rows=99935 loops=1)
         Index Cond: ((id >= 66) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 91.207 ms
 Execution time: 663.920 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 66 and 100000 and val != '';
                                                        QUERY PLAN                                                        
--------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=80.395..5564.713 rows=99935 loops=1)
   Recheck Cond: ((id >= 66) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1538
   Buffers: shared read=1813
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=79.775..79.775 rows=99935 loops=1)
         Index Cond: ((id >= 66) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 43.715 ms
 Execution time: 5571.118 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 66 and 100000 and val != '';
                                                         QUERY PLAN                                                         
----------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=211.112..677.029 rows=99935 loops=1)
   Recheck Cond: ((id >= 66) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1538
   Buffers: shared read=1813
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=210.187..210.187 rows=99935 loops=1)
         Index Cond: ((id >= 66) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 84.665 ms
 Execution time: 683.056 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 66 and 100000 and val != '';
                                                        QUERY PLAN                                                        
--------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=50.186..5877.018 rows=99935 loops=1)
   Recheck Cond: ((id >= 66) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1538
   Buffers: shared read=1813
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=49.238..49.238 rows=99935 loops=1)
         Index Cond: ((id >= 66) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 50.967 ms
 Execution time: 5883.359 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 66 and 100000 and val != '';
                                                        QUERY PLAN                                                        
--------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=70.832..466.732 rows=99935 loops=1)
   Recheck Cond: ((id >= 66) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1538
   Buffers: shared read=1813
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=69.865..69.865 rows=99935 loops=1)
         Index Cond: ((id >= 66) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 71.727 ms
 Execution time: 472.809 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 66 and 100000 and val != '';
                                                        QUERY PLAN                                                        
--------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on test  (cost=7.62..467.66 rows=498 width=36) (actual time=82.587..5453.616 rows=99935 loops=1)
   Recheck Cond: ((id >= 66) AND (id <= 100000))
   Filter: (val <> ''::text)
   Heap Blocks: exact=1538
   Buffers: shared read=1813
   ->  Bitmap Index Scan on test_pkey  (cost=0.00..7.49 rows=500 width=0) (actual time=69.489..69.489 rows=99935 loops=1)
         Index Cond: ((id >= 66) AND (id <= 100000))
         Buffers: shared read=275
 Planning time: 80.914 ms
 Execution time: 5461.794 ms
(10 rows)

