QUERY PLAN                                                                          
-------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=766983.18..767070.52 rows=100 width=498) (actual time=5508.261..5508.532 rows=100 loops=1)
   Buffers: shared hit=30249 read=342473, temp read=16856 written=28392
   ->  Merge Join  (cost=766983.18..2008284.16 rows=1421289 width=498) (actual time=5508.260..5508.527 rows=100 loops=1)
         Merge Cond: ((books.asin)::text = (asins.value)::text)
         Buffers: shared hit=30249 read=342473, temp read=16856 written=28392
         ->  Index Scan using books_asin_key on books  (cost=0.43..1216522.35 rows=1403453 width=333) (actual time=0.007..0.150 rows=100 loops=1)
               Buffers: shared hit=103
         ->  Materialize  (cost=766980.48..774092.68 rows=1422439 width=155) (actual time=5508.248..5508.304 rows=100 loops=1)
               Buffers: shared hit=30146 read=342473, temp read=16856 written=28392
               ->  Sort  (cost=766980.48..770536.58 rows=1422439 width=155) (actual time=5508.245..5508.293 rows=100 loops=1)
                     Sort Key: asins.value
                     Sort Method: external merge  Disk: 136864kB
                     Buffers: shared hit=30146 read=342473, temp read=16856 written=28392
                     ->  Hash Join  (cost=55734.25..509782.68 rows=1422439 width=155) (actual time=412.394..2071.400 rows=1404582 loops=1)
                           Hash Cond: (asins_statistics.asin_id = asins.id)
                           Buffers: shared hit=30146 read=342473, temp read=11281 written=11279
                           ->  Seq Scan on asins_statistics  (cost=0.00..373686.39 rows=1422439 width=120) (actual time=0.005..782.893 rows=1404582 loops=1)
                                 Buffers: shared hit=16989 read=342473
                           ->  Hash  (cost=27202.89..27202.89 rows=1404589 width=35) (actual time=412.025..412.026 rows=1404589 loops=1)
                                 Buckets: 1048576  Batches: 2  Memory Usage: 51393kB
                                 Buffers: shared hit=13157, temp written=4363
                                 ->  Seq Scan on asins  (cost=0.00..27202.89 rows=1404589 width=35) (actual time=0.010..151.754 rows=1404589 loops=1)
                                       Buffers: shared hit=13157
 Planning time: 0.770 ms
 Execution time: 5525.959 ms
(25 rows)



SET enable_seqscan = OFF;


                                                                                    QUERY PLAN                                                                                    
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=10001314403.06..10001314490.39 rows=100 width=498) (actual time=6171.243..6171.489 rows=100 loops=1)
   Buffers: shared hit=1030733 read=346050, temp read=22327 written=34044
   ->  Merge Join  (cost=10001314403.06..10002555704.04 rows=1421289 width=498) (actual time=6171.241..6171.478 rows=100 loops=1)
         Merge Cond: ((books.asin)::text = (asins.value)::text)
         Buffers: shared hit=1030733 read=346050, temp read=22327 written=34044
         ->  Index Scan using books_asin_key on books  (cost=0.43..1216522.35 rows=1403453 width=333) (actual time=0.019..0.144 rows=100 loops=1)
               Buffers: shared hit=103
         ->  Materialize  (cost=10001314400.36..10001321512.55 rows=1422439 width=155) (actual time=6171.213..6171.265 rows=100 loops=1)
               Buffers: shared hit=1030630 read=346050, temp read=22327 written=34044
               ->  Sort  (cost=10001314400.36..10001317956.46 rows=1422439 width=155) (actual time=6171.133..6171.178 rows=100 loops=1)
                     Sort Key: asins.value
                     Sort Method: external merge  Disk: 136864kB
                     Buffers: shared hit=1030630 read=346050, temp read=22327 written=34044
                     ->  Hash Join  (cost=10000416471.30..10001057202.55 rows=1422439 width=155) (actual time=1074.832..2719.409 rows=1404582 loops=1)
                           Hash Cond: (asins.id = asins_statistics.asin_id)
                           Buffers: shared hit=1030630 read=346050, temp read=16937 written=16931
                           ->  Index Scan using isbns_pkey on asins  (cost=0.43..574466.58 rows=1404589 width=35) (actual time=0.012..688.506 rows=1404589 loops=1)
                                 Buffers: shared hit=1015561 read=1657
                           ->  Hash  (cost=10000373686.39..10000373686.39 rows=1422439 width=120) (actual time=1065.611..1065.611 rows=1404582 loops=1)
                                 Buckets: 524288  Batches: 4  Memory Usage: 35931kB
                                 Buffers: shared hit=15069 read=344393, temp written=10377
                                 ->  Seq Scan on asins_statistics  (cost=10000000000.00..10000373686.39 rows=1422439 width=120) (actual time=0.025..795.542 rows=1404582 loops=1)
                                       Buffers: shared hit=15069 read=344393
 Planning time: 1.128 ms
 Execution time: 6189.046 ms
(25 rows)




SET enable_sort = OFF;

Query takes a lot of time.