Jesus Camacho Rodriguez created HIVE-16102:
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Summary: Grouping sets do not conform to SQL standard
Key: HIVE-16102
URL: https://issues.apache.org/jira/browse/HIVE-16102
Project: Hive
Issue Type: Bug
Components: Operators, Parser
Affects Versions: 1.3.0, 2.2.0
Reporter: Jesus Camacho Rodriguez
Assignee: Jesus Camacho Rodriguez
[~ashutoshc] realized that the implementation of GROUPING__ID in Hive was not
returning values as specified by SQL standard and other execution engines.
After digging into this, I found out that the implementation was bogus, as
internally it was changing between big-endian/little-endian representation of
GROUPING__ID indistinctly, and in some cases conversions in both directions
were cancelling each other.
In the documentation in
https://cwiki.apache.org/confluence/display/Hive/Enhanced+Aggregation,+Cube,+Grouping+and+Rollup
we can already find the problem, even if we did not spot it at first.
{quote}
The following query: SELECT key, value, GROUPING__ID, count(\*) from T1 GROUP
BY key, value WITH ROLLUP
will have the following results.
| NULL | NULL | 0 | 6 |
| 1 | NULL | 1 | 2 |
| 1 | NULL | 3 | 1 |
| 1 | 1 | 3 | 1 |
...
{quote}
Observe that value for GROUPING__ID in first row should be `3`, while for
second and third rows, it should be `0`.
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