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Posted to dev@hive.apache.org by "Steve Carlin (Jira)" <ji...@apache.org> on 2022/10/27 02:00:00 UTC

[jira] [Created] (HIVE-26672) Top N Key Operator should not be allowed to pass through group by with grouping sets

Steve Carlin created HIVE-26672:
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             Summary: Top N Key Operator should not be allowed to pass through group by with grouping sets
                 Key: HIVE-26672
                 URL: https://issues.apache.org/jira/browse/HIVE-26672
             Project: Hive
          Issue Type: Bug
          Components: Operators
            Reporter: Steve Carlin


HIVE-22652 enabled the Top N Key operator to be pushed down through a group by with grouping sets, but I think I have an example where this isn't correct.

If I take the following query:

SELECT a, b, sum(c) FROM t_test_grouping_sets GROUP BY a,b GROUPING SETS (()) ORDER BY b DESC  LIMIT 1;

If we were to push the Top N Key operator all the way to the top, it would produce incorrect results.   We need to calculate the sum for all rows in the query, so we don't want to limit the rows that are passed through.



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