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Posted to issues@arrow.apache.org by "jorisvandenbossche (via GitHub)" <gi...@apache.org> on 2023/05/30 09:08:47 UTC

[GitHub] [arrow] jorisvandenbossche opened a new issue, #35817: [Docs][C++] "value_counts" kernel doc incorrectly mentions to skip nulls

jorisvandenbossche opened a new issue, #35817:
URL: https://github.com/apache/arrow/issues/35817

   The "value_counts" kernel indicates that nulls in the input are skipped:
   
   https://github.com/apache/arrow/blob/431785f3062199b2b9052902b67492b933744833/cpp/src/arrow/compute/kernels/vector_hash.cc#L748-L753
   
   But that's not actually the case. Nulls are also counted and included in the output:
   
   ```python
   In [1]: import pyarrow.compute as pc
   
   In [2]: pc.value_counts([1, 2, 2, None, None])
   Out[2]: 
   <pyarrow.lib.StructArray object at 0x7fb88e1c6f20>
   -- is_valid: all not null
   -- child 0 type: int64
     [
       1,
       2,
       null
     ]
   -- child 1 type: int64
     [
       1,
       2,
       2
     ]
   ```


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[GitHub] [arrow] pitrou closed issue #35817: [Docs][C++] "value_counts" kernel doc incorrectly mentions to skip nulls

Posted by "pitrou (via GitHub)" <gi...@apache.org>.
pitrou closed issue #35817: [Docs][C++] "value_counts" kernel doc incorrectly mentions to skip nulls
URL: https://github.com/apache/arrow/issues/35817


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[GitHub] [arrow] jorisvandenbossche commented on issue #35817: [Docs][C++] "value_counts" kernel doc incorrectly mentions to skip nulls

Posted by "jorisvandenbossche (via GitHub)" <gi...@apache.org>.
jorisvandenbossche commented on issue #35817:
URL: https://github.com/apache/arrow/issues/35817#issuecomment-1568071013

   Same is true for `unique`:
   
   ```
   In [3]: pc.unique([1, 2, 2, None, None])
   Out[3]: 
   <pyarrow.lib.Int64Array object at 0x7fb88e1c75e0>
   [
     1,
     2,
     null
   ]
   ```
   
   And to show it's just the docs, we have various tests that cover this.
   


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