[C++] Usage of Hash Aggregation

[ava6969]

Describe the usage question you have. Please include as many useful details as possible.

I am still confused on the right way to use the hash aggregations. I found 3 different approaches in the hash_aggregation_test.cc which included a naive grouper/exec_plan and internal group_by. Is anyone particularly recommended as GroupBy is used in the python api but the doc said its not for public use.

Component(s)

C++

[westonpace]

My opinion is that the correct approach should be to use an exec plan. Pyarrow perhaps uses internal::GroupBy because it finds the API more convenient but it was never intended to be a long term thing.

I have a PR (#14867) to adapt the internal::GroupBy API to using an exec plan under the hood for those that find that API more convenient. However, this PR is not yet merged.

[ava6969]

Thanks for your clarification i'll check it out.