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
----------------------------------------------------------------------------------------------------------------------------------------
 Insert on public.testscan  (cost=3272.20..3652841.26 rows=0 width=0) (actual time=360.474..360.476 rows=0 loops=1)
   Buffers: shared hit=392569 read=3 dirtied=934 written=933
   WAL: records=260354 bytes=16259841
   ->  Bitmap Heap Scan on public.x  (cost=3272.20..3652841.26 rows=79918 width=8) (actual time=8.096..41.005 rows=129999 loops=1)
         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: 50000
         Heap Blocks: exact=975
         Buffers: shared hit=1475
         ->  BitmapOr  (cost=3272.20..3272.20 rows=174813 width=0) (actual time=7.975..7.976 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=3.469..3.470 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=4.499..4.499 rows=100000 loops=1)
                     Index Cond: (x.a > 199900000)
                     Buffers: shared hit=278
 Planning:
   Buffers: shared hit=10
 Planning Time: 0.126 ms
 Execution Time: 360.547 ms
(22 rows)