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  1. Hive
  2. HIVE-16298

Add config to specify multi-column joins have correlated columns

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Details

    • Bug
    • Status: Closed
    • Major
    • Resolution: Fixed
    • None
    • 3.0.0
    • None

    Description

      The default row estimation for multi-key joins divides the row estimate by the product of the NDVs for each join column, which can cause the row estimate to be low. Try adding a config to assume the columns are correlated, where we only divide the row estimate by the largest NDV.

      Attachments

        1. HIVE-16298.1.patch
          16 kB
          Jason Dere
        2. HIVE-16298.2.patch
          16 kB
          Jason Dere

        Issue Links

        is related to

        Bug - A problem which impairs or prevents the functions of the product. HIVE-20537 Multi-column joins estimates with uncorrelated columns different in CBO and Hive

        • Major - Major loss of function.
        • Closed

        Improvement - An improvement or enhancement to an existing feature or task. HIVE-17308 Improvement in join cardinality estimation

        • Major - Major loss of function.
        • Closed

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          People

            sseth Siddharth Seth Assign to me
            jdere Jason Dere
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              Updated:
              Resolved:

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