with parallel_leader_participation = 1;
                                                                                                     QUERY PLAN                                                                                          
             
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-------------
 Limit  (cost=1001.19..504469.79 rows=1 width=27) (actual time=21833.206..21833.207 rows=1 loops=1)
   ->  GroupAggregate  (cost=1001.19..3525281.42 rows=7 width=27) (actual time=21833.203..21833.203 rows=1 loops=1)
         Group Key: lineitem.l_shipmode
         ->  Gather Merge  (cost=1001.19..3515185.81 rows=576888 width=27) (actual time=4.388..21590.757 rows=311095 loops=1)
               Workers Planned: 4
               Workers Launched: 4
               ->  Nested Loop  (cost=1.13..3445472.82 rows=144222 width=27) (actual time=0.150..4399.384 rows=62247 loops=5)
                     ->  Parallel Index Scan using l_shipmode on lineitem  (cost=0.57..3337659.69 rows=144222 width=19) (actual time=0.111..3772.865 rows=62247 loops=5)
                           Index Cond: (l_shipmode = ANY ('{"REG AIR",RAIL}'::bpchar[]))
                           Filter: ((l_commitdate < l_receiptdate) AND (l_shipdate < l_commitdate) AND (l_receiptdate >= '1995-01-01'::date) AND (l_receiptdate < '1996-01-01 00:00:00'::timestamp without
 time zone))
                           Rows Removed by Filter: 3367603
                     ->  Index Scan using orders_pkey on orders  (cost=0.56..0.75 rows=1 width=20) (actual time=0.009..0.009 rows=1 loops=311236)
                           Index Cond: (o_orderkey = lineitem.l_orderkey)
 Planning time: 0.526 ms
 Execution time: 21835.922 ms
(15 rows)

postgres=# set parallel_leader_participation =0;
SET
postgres=# \i /data/rafia.sabih/dss/queries/12.sql 
                                                                                                      QUERY PLAN                                                                                          
             
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-------------
 Limit  (cost=1001.19..504469.79 rows=1 width=27) (actual time=21179.065..21179.066 rows=1 loops=1)
   ->  GroupAggregate  (cost=1001.19..3525281.42 rows=7 width=27) (actual time=21179.064..21179.064 rows=1 loops=1)
         Group Key: lineitem.l_shipmode
         ->  Gather Merge  (cost=1001.19..3515185.81 rows=576888 width=27) (actual time=4.201..20941.385 rows=311095 loops=1)
               Workers Planned: 4
               Workers Launched: 4
               ->  Nested Loop  (cost=1.13..3445472.82 rows=144222 width=27) (actual time=0.187..5105.780 rows=77797 loops=4)
                     ->  Parallel Index Scan using l_shipmode on lineitem  (cost=0.57..3337659.69 rows=144222 width=19) (actual time=0.149..4362.235 rows=77797 loops=4)
                           Index Cond: (l_shipmode = ANY ('{"REG AIR",RAIL}'::bpchar[]))
                           Filter: ((l_commitdate < l_receiptdate) AND (l_shipdate < l_commitdate) AND (l_receiptdate >= '1995-01-01'::date) AND (l_receiptdate < '1996-01-01 00:00:00'::timestamp without
 time zone))
                           Rows Removed by Filter: 4208802
                     ->  Index Scan using orders_pkey on orders  (cost=0.56..0.75 rows=1 width=20) (actual time=0.008..0.008 rows=1 loops=311187)
                           Index Cond: (o_orderkey = lineitem.l_orderkey)
 Planning time: 0.443 ms
 Execution time: 21183.148 ms
(15 rows)