[GitHub] [arrow] coady opened a new issue, #36149: `table.group_by([]).aggregate` raises an error on some aggregate functions.

["coady (via GitHub)" <gi...@apache.org>]

coady opened a new issue, #36149:
URL: https://github.com/apache/arrow/issues/36149

   ### Describe the bug, including details regarding any error messages, version, and platform.
   
   Grouping on empty keys aggregates against the whole table (relates to #14896).  But there are 3 hash aggregate functions which do not have corresponding scalar aggregate functions: `hash_distinct`, `hash_list`, and `hash_one`. Grouping on empty keys with those raises a key error.
   ```python
   In []: table = pa.table({'key': list('aba'), 'value': [0, 1, 2]})
   
   In []: table.group_by(['key']).aggregate([('value', 'list')])
   Out[]: 
   pyarrow.Table
   key: string
   value_list: list<item: int64>
     child 0, item: int64
   ----
   key: [["a","b"]]
   value_list: [[[0,2],[1]]]
   
   In []: table.group_by([]).aggregate([('value', 'list')])
   ...
   ArrowKeyError: No function registered with name: list
   
   In []: table.group_by([]).aggregate([('value', 'min')])
   Out[]: 
   pyarrow.Table
   value_min: int64
   ----
   value_min: [[0]]
   ```
   
   
   ### Component(s)
   
   C++, Python


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[GitHub] [arrow] vibhatha commented on issue #36149: `table.group_by([]).aggregate` raises an error on some aggregate functions.

["vibhatha (via GitHub)" <gi...@apache.org>]

vibhatha commented on issue #36149:
URL: https://github.com/apache/arrow/issues/36149#issuecomment-1634422769

   take


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