[GitHub] [arrow] ianmcook commented on a change in pull request #12463: ARROW-15717: [Docs] Add hash_one to the documentation

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ianmcook commented on a change in pull request #12463:
URL: https://github.com/apache/arrow/pull/12463#discussion_r810100430



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File path: docs/source/cpp/compute.rst
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@@ -371,12 +373,17 @@ equivalents above and reflects how they are implemented internally.
   Of the interval types, only the month interval is supported, as the day-time
   and month-day-nano types are not sortable.
 
-* \(5) Output is Int64, UInt64, Float64, or Decimal128/256, depending on the
+* \(5) The function is biased towards non-null values. That is, if there is
+  at least one non-null value in a certain group, that value is returned,
+  and only if all the values are ``null`` for the group,
+  will the aggregate(``hash_one``) value be ``null``. 

Review comment:
       Users might not recognize what this function does by its name, so I think we should include more information in the note:
   ```suggestion
   * \(5) ``hash_one`` returns one arbitrary value from the input for each
     group. The function is biased towards non-null values: if there is at least
     one non-null value for a certain group, that value is returned, and only if
     all the values are ``null`` for the group will the function return ``null``. 
   ```




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