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
-------------------------------------------------------------------------------------------------------------------------------------------------
 Gather  (cost=4272.20..1269111.15 rows=79918 width=0) (actual time=381.764..382.715 rows=0 loops=1)
   Workers Planned: 4
   Workers Launched: 4
   Buffers: shared hit=407094 read=4 dirtied=1085 written=1158
   WAL: records=260498 bytes=17019359
   ->  Insert on public.testscan  (cost=3272.20..1260119.35 rows=0 width=0) (actual time=378.227..378.229 rows=0 loops=5)
         Buffers: shared hit=407094 read=4 dirtied=1085 written=1158
         WAL: records=260498 bytes=17019359
         Worker 0:  actual time=376.638..376.640 rows=0 loops=1
           Buffers: shared hit=88281 dirtied=236 written=337
           WAL: records=56167 bytes=3674994
         Worker 1:  actual time=377.889..377.892 rows=0 loops=1
           Buffers: shared hit=81231 dirtied=213 written=99
           WAL: records=52175 bytes=3386885
         Worker 2:  actual time=377.388..377.389 rows=0 loops=1
           Buffers: shared hit=82544 dirtied=232 written=279
           WAL: records=52469 bytes=3443843
         Worker 3:  actual time=377.733..377.734 rows=0 loops=1
           Buffers: shared hit=87728 dirtied=225 written=182
           WAL: records=56307 bytes=3660758
         ->  Parallel Bitmap Heap Scan on public.x  (cost=3272.20..1260119.35 rows=19980 width=8) (actual time=5.832..14.787 rows=26000 loops=5)
               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: 10000
               Heap Blocks: exact=167
               Buffers: shared hit=1475
               Worker 0:  actual time=5.203..14.921 rows=28028 loops=1
                 Buffers: shared hit=209
               Worker 1:  actual time=5.165..14.403 rows=26039 loops=1
                 Buffers: shared hit=196
               Worker 2:  actual time=5.188..14.284 rows=26177 loops=1
                 Buffers: shared hit=195
               Worker 3:  actual time=5.151..14.760 rows=28104 loops=1
                 Buffers: shared hit=208
               ->  BitmapOr  (cost=3272.20..3272.20 rows=174813 width=0) (actual time=8.288..8.290 rows=0 loops=1)
                     Buffers: shared hit=500
                     ->  Bitmap Index Scan on x_a_idx  (cost=0.00..1468.38 rows=79441 width=0) (actual time=3.681..3.681 rows=79999 loops=1)
                           Index Cond: (x.a < 80000)
                           Buffers: shared hit=222
                     ->  Bitmap Index Scan on x_a_idx  (cost=0.00..1763.86 rows=95372 width=0) (actual time=4.605..4.605 rows=100000 loops=1)
                           Index Cond: (x.a > 199900000)
                           Buffers: shared hit=278
 Planning:
   Buffers: shared hit=19
 Planning Time: 0.173 ms
 Execution Time: 382.776 ms
(47 rows)

Execuse me, tsunakawa san, sorry to bother you,
 May I ask you some questions ?

>[1]
>Add accumulated statistics for wait event https://commitfest.postgresql.org/28/2332/

I remembered FEP has such feature, is this the same as FEP.

Ok. thanks a lot for the explanation.
BTW, I am sorry the tablename I tested today is different from yesterday,
It may confused you, I have check that the result of both is the same.