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Posted to jira@arrow.apache.org by "A. Coady (Jira)" <ji...@apache.org> on 2022/02/20 22:49:00 UTC

[jira] [Created] (ARROW-15735) [C++] Hash aggregate functions to return first and last value from a group.

A. Coady created ARROW-15735:
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             Summary: [C++] Hash aggregate functions to return first and last value from a group.
                 Key: ARROW-15735
                 URL: https://issues.apache.org/jira/browse/ARROW-15735
             Project: Apache Arrow
          Issue Type: New Feature
          Components: C++
            Reporter: A. Coady


Follow-up to ARROW-13993, which implemented `hash_one` to select an arbitrary value, as the core engine lack support for ordering. I think `first` and `last` will still be in demand though, based on pandas and sql usage.

It could be done without core changes by using `min_max` on an array of indices. For that reason, maybe it would be better as `hash_\{first,last}_index`, suitable for use with `take`.



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