portal=# create table bulk_data (a integer, b integer, primary key (a, b));     NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "bulk_data_pkey" for table "bulk_data"
CREATE TABLE
portal=# insert into bulk_data select 1,generate_series(1,1000000);             INSERT 0 1000000
portal=# insert into bulk_data select 2,generate_series(1,1000000);
INSERT 0 1000000
portal=# explain analyze select * from bulk_data where a = 1 limit 100;                                                                        QUERY PLAN       
-----------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.00..272.33 rows=100 width=8) (actual time=0.461..0.875 rows=100 loops=1)
   ->  Index Scan using bulk_data_pkey on bulk_data  (cost=0.00..25898.89 rows=9510 width=8) (actual time=0.454..0.630 rows=100 loops=1)
         Index Cond: (a = 1)
 Total runtime: 1.094 ms
(4 rows)

portal=# explain analyze select * from bulk_data where a = 1 and (b % 1000) = 0 limit 100;
                                                                 QUERY PLAN     
--------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=183.81..10439.27 rows=48 width=8) (actual time=409.110..494.701 rows=100 loops=1)
   ->  Bitmap Heap Scan on bulk_data  (cost=183.81..10439.27 rows=48 width=8) (actual time=409.103..494.228 rows=100 loops=1)
         Recheck Cond: (a = 1)
         Filter: ((b % 1000) = 0)
         ->  Bitmap Index Scan on bulk_data_pkey  (cost=0.00..183.79 rows=9510 width=0) (actual time=404.616..404.616 rows=1000000 loops=1)
               Index Cond: (a = 1)
 Total runtime: 495.186 ms
(7 rows)

portal=# analyze bulk_data;
ANALYZE
portal=# explain analyze select * from bulk_data where a = 1 limit 100;                                                              QUERY PLAN                 
--------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.00..3.50 rows=100 width=8) (actual time=0.037..0.435 rows=100 loops=1)
   ->  Seq Scan on bulk_data  (cost=0.00..34804.20 rows=995341 width=8) (actual time=0.031..0.184 rows=100 loops=1)
         Filter: (a = 1)
 Total runtime: 0.676 ms
(4 rows)

portal=# explain analyze select * from bulk_data where a = 1 and (b % 1000) = 0 limit 100;
                                                    QUERY PLAN                  
-------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.00..900.23 rows=100 width=8) (actual time=1.261..76.754 rows=100 loops=1)
   ->  Seq Scan on bulk_data  (cost=0.00..44804.28 rows=4977 width=8) (actual time=1.255..76.381 rows=100 loops=1)
         Filter: ((a = 1) AND ((b % 1000) = 0))
 Total runtime: 77.084 ms
(4 rows)

portal=#