[I] Incorrect results when using grouping sets with data containing nulls [datafusion]

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

eejbyfeldt opened a new issue, #12570:
URL: https://github.com/apache/datafusion/issues/12570

   ### Describe the bug
   
   When doing a grouping set on columns with null values we produce the incorrect result.
   
   ### To Reproduce
   
   Run the following in query in datafusion-cli
   ```
   > CREATE TABLE integers_with_nulls (value INT) as VALUES (1), (NULL);
   
   0 row(s) fetched. 
   Elapsed 0.016 seconds.
   
   > SELECT value, min(value) FROM integers_with_nulls GROUP BY CUBE(value);
   
   +-------+--------------------------------+
   | value | min(integers_with_nulls.value) |
   +-------+--------------------------------+
   | 1     | 1                              |
   |       | 1                              |
   +-------+--------------------------------+
   ```
   
   ### Expected behavior
   
   The expected bevahior is that the null in the data creates a different group from the nulls from the grouping set. The exected results are
   ```
   > SELECT value, min(value) FROM integers_with_nulls GROUP BY CUBE(value);
   +-------+--------------------------------+
   | value | min(integers_with_nulls.value) |
   +-------+--------------------------------+
   | 1     | 1                              |
   |       | 1                              |
   |       |                                |
   +-------+--------------------------------+
   ```
   This is the behavior in PostgresSQL, Spark and DuckDB (and most likely other query engines).
   
   ### Additional context
   
   _No response_


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