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Posted to dev@hive.apache.org by "Jesus Camacho Rodriguez (JIRA)" <ji...@apache.org> on 2016/02/18 21:56:18 UTC

[jira] [Created] (HIVE-13089) Rounding in Stats for equality expressions

Jesus Camacho Rodriguez created HIVE-13089:
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             Summary: Rounding in Stats for equality expressions
                 Key: HIVE-13089
                 URL: https://issues.apache.org/jira/browse/HIVE-13089
             Project: Hive
          Issue Type: Bug
          Components: Statistics
    Affects Versions: 2.1.0
            Reporter: Jesus Camacho Rodriguez
            Assignee: Jesus Camacho Rodriguez


Currently we divide numRows(long) by countDistinct(long), thus ignoring the decimals. We should do proper rounding.

This is specially useful for equality expressions over columns whose values are unique. As NDV estimates allow for a certain error, if countDistinct > numRows, we end up with 0 rows in the estimate for the expression.



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