On Mon, Feb 8, 2021 at 8:13 PM Hou, Zhijie <houzj.f...@cn.fujitsu.com> wrote: > > > > Did it actually use a parallel plan in your testing? > > > When I ran these tests with the Parallel INSERT patch applied, it did > > > not naturally choose a parallel plan for any of these cases. > > > > Yes, these cases pick parallel plan naturally on my test environment. > > > > postgres=# explain verbose insert into testscan select a from x where > > a<80000 or (a%2=0 and a>199900000); > > QUERY PLAN > > ---------------------------------------------------------------------- > > ----------------------------- > > Gather (cost=4346.89..1281204.64 rows=81372 width=0) > > Workers Planned: 4 > > -> Insert on public.testscan (cost=3346.89..1272067.44 rows=0 > > width=0) > > -> Parallel Bitmap Heap Scan on public.x1 > > (cost=3346.89..1272067.44 rows=20343 width=8) > > Output: x1.a, NULL::integer > > Recheck Cond: ((x1.a < 80000) OR (x1.a > 199900000)) > > Filter: ((x1.a < 80000) OR (((x1.a % 2) = 0) AND (x1.a > > > 199900000))) > > -> BitmapOr (cost=3346.89..3346.89 rows=178808 > > width=0) > > -> Bitmap Index Scan on x1_a_idx > > (cost=0.00..1495.19 rows=80883 width=0) > > Index Cond: (x1.a < 80000) > > -> Bitmap Index Scan on x1_a_idx > > (cost=0.00..1811.01 rows=97925 width=0) > > Index Cond: (x1.a > 199900000) > > > > PSA is my postgresql.conf file, maybe you can have a look. Besides, I didn't > > do any parameters tuning in my test session. > > I reproduced this on my machine. > > I think we'd better do "analyze" before insert which helps reproduce this > easier. > Like: > > ----- > analyze; > explain analyze verbose insert into testscan select a from x where a<80000 or > (a%2=0 and a>199900000); > -----
OK then. Can you check if just the underlying SELECTs are run (without INSERT), is there any performance degradation when compared to a non-parallel scan? Regards, Greg Nancarrow Fujitsu Australia
