Dear all,

I wonder what the best way forward is for implementing GroupBy kernels. Initially this was part of

https://issues.apache.org/jira/browse/ARROW-4124

but is not contained in the current implementation as far as I can tell.

It seems that the part of group by that just returns indices could be conveniently implemented with the HashKernel. That seems useful in any case. Is that indeed the best way forward/should this be done?

GroupBy + Aggregate could then either be implemented with that + the Take kernel + aggregation involving more memory copies than necessary though or as part of the aggregate kernel. Probably the latter is preferred, any thoughts on that?

Am I missing any other JIRAs related to this?

Best, Philipp.

Reporter: Philipp Moritz / @pcmoritz

Related issues:

• [C++] Parallelize execution of ScalarAggregateFunction (blocks)
• cpp implementation for hash aggregation and binding in python (is duplicated by)
• [C++][Compute] Wrap grouped aggregation in an ExecNode (depends upon)

_{Note: This issue was originally created as ARROW-5002. Please see the migration documentation for further details.}