postgres=# explain (ANALYZE, BUFFERS, VERBOSE, WAL)  insert into testscan select a from x where a<80000 or (a%2=0 and a>199900000);
                                                                   QUERY PLAN

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 Gather  (cost=4258.59..2063373.72 rows=81338 width=0) (actual time=0.203..310.184 rows=0 loops=1)
   Workers Planned: 2
   Workers Launched: 2
   Buffers: shared hit=393777 read=4 dirtied=939 written=953
   WAL: records=260356 bytes=16281081
   ->  Insert on public.testscan  (cost=3258.59..2054239.92 rows=0 width=0) (actual time=305.474..305.476 rows=0 loops=2)
         Buffers: shared hit=393777 read=4 dirtied=939 written=953
         WAL: records=260356 bytes=16281081
         Worker 0:  actual time=305.378..305.379 rows=0 loops=1
           Buffers: shared hit=196680 read=3 dirtied=462 written=478
           WAL: records=130155 bytes=8129880
         Worker 1:  actual time=305.570..305.572 rows=0 loops=1
           Buffers: shared hit=197097 read=1 dirtied=477 written=475
           WAL: records=130201 bytes=8151201
         ->  Parallel Bitmap Heap Scan on public.x  (cost=3258.59..2054239.92 rows=40669 width=8) (actual time=8.883..27.998 rows=65000 loops=2)
               Output: x.a, NULL::integer
               Recheck Cond: ((x.a < 80000) OR (x.a > 199900000))
               Filter: ((x.a < 80000) OR (((x.a % 2) = 0) AND (x.a > 199900000)))
               Rows Removed by Filter: 25000
               Buffers: shared hit=1476
               Worker 0:  actual time=8.796..27.982 rows=64992 loops=1
                 Buffers: shared hit=487
               Worker 1:  actual time=8.971..28.014 rows=65007 loops=1
                 Buffers: shared hit=989
               ->  BitmapOr  (cost=3258.59..3258.59 rows=173971 width=0) (actual time=8.810..8.811 rows=0 loops=1)
                     Buffers: shared hit=501
                     Worker 1:  actual time=8.810..8.811 rows=0 loops=1
                       Buffers: shared hit=501
                     ->  Bitmap Index Scan on x_a_idx  (cost=0.00..1495.11 rows=80872 width=0) (actual time=3.832..3.832 rows=79999 loops=1)
                           Index Cond: (x.a < 80000)
                           Buffers: shared hit=223
                           Worker 1:  actual time=3.832..3.832 rows=79999 loops=1
                             Buffers: shared hit=223
                     ->  Bitmap Index Scan on x_a_idx  (cost=0.00..1722.81 rows=93099 width=0) (actual time=4.976..4.976 rows=100000 loops=1)
                           Index Cond: (x.a > 199900000)
                           Buffers: shared hit=278
                           Worker 1:  actual time=4.976..4.976 rows=100000 loops=1
                             Buffers: shared hit=278
 Planning:
   Buffers: shared hit=19
 Planning Time: 0.146 ms
 Execution Time: 310.257 ms
(42 rows)