Re: Hybrid Hash/Nested Loop joins and caching results from subplans

Today I tested the correctness & performance of this patch based on TPC-H
workload, the environment is setup based on [1]. Correctness is tested by
storing the result into another table when this feature is not introduced
and
then enable this feature and comparing the result with the original ones. No
issue is found at this stage.

I also checked the performance gain for TPC-H workload, totally 4 out of
the 22
queries uses this new path, 3 of them are subplan, 1 of them is nestloop.
All of
changes gets a better result. You can check the attachments for reference.
normal.log is the data without this feature, patched.log is the data with
the
feature. The data doesn't show the 10x performance gain, I think that's
mainly
data size related.

At the code level, I mainly checked nestloop path and
cost_resultcache_rescan,
everything looks good to me. I'd like to check the other parts in the
following days.

[1] https://ankane.org/tpc-h

--
Best Regards
Andy Fan