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Incorrect results when using grouping sets with data containing nulls #12570

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eejbyfeldt opened this issue Sep 21, 2024 · 0 comments · Fixed by #12571
Closed

Incorrect results when using grouping sets with data containing nulls #12570

eejbyfeldt opened this issue Sep 21, 2024 · 0 comments · Fixed by #12571
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@eejbyfeldt
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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

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fix: Correct results for grouping sets when columns contain nulls eejbyfeldt/datafusion
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@eejbyfeldt