[GitHub] [arrow] Crystrix opened a new pull request #12251: ARROW-15441: [C++] Fix incorrect result of hash_count a null type column

[GitBox]

Crystrix opened a new pull request #12251:
URL: https://github.com/apache/arrow/pull/12251


   The result of hash_count such array is incorrect.
   For a table like this:
   <table>
   <thead>
   <tr>
   <th>argument</th>
   <th>key</th>
   </tr>
   </thead>
   <tbody>
   <tr>
   <td>NULL</td>
   <td>1</td>
   </tr>
   <tr>
   <td>NULL</td>
   <td>1</td>
   </tr>
   </tbody>
   </table>
   
   The result is :
   <table>
   <thead>
   <tr>
   <th>CountOptions</th>
   <th>Expected</th>
   <th>Actual</th>
   </tr>
   </thead>
   <tbody>
   <tr>
   <td>ONLY_VALID</td>
   <td>0</td>
   <td>2</td>
   </tr>
   <tr>
   <td>ONLY_NULL</td>
   <td>2</td>
   <td>0</td>
   </tr>
   </tbody>
   </table>
   
   This PR handles null type with different count options.
   
   


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