RE: Parallel INSERT (INTO ... SELECT ...)

Hi Greg,

Recently, I was keeping evaluating performance of this patch(1/28 V13).
Here I find a regression test case which is parallel insert with bitmap heap scan.
when the target table has primary key or index, then the patched performance will have a 7%-19% declines than
unpatched.
 

Could you please have a look about this?

I tried max_parallel_workers_per_gather=2/4/8, and I didn't tune other parameters(like GUCs or other enforce parallel
parameters).
 

1. max_parallel_workers_per_gather=2(default)
target_table        patched       master      %reg
------------------------------------------------------
without_PK_index    83.683        142.183    -41%
with_PK             382.824       321.101    19%
with_index          372.682       324.246    15%

2. max_parallel_workers_per_gather=4
target_table        patched       master      %reg
------------------------------------------------------
without_PK_index    73.189        141.879     -48%
with_PK             362.104       329.759     10%
with_index          372.237       333.718     12%

3. max_parallel_workers_per_gather=8 (also set max_parallel_workers=16, max_worker_processes = 16)
target_table        patched       master      %reg
------------------------------------------------------
without_PK_index    75.072        146.100     -49%
with_PK             365.312       324.339     13%
with_index          362.636       338.366     7%

Attached test_bitmap.sql which includes my test data and sql if you want to have a look. 

Regards,
Tang