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  1. Hive
  2. HIVE-10568

Select count(distinct()) can have more optimal execution plan

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Details

    • Improvement
    • Status: Closed
    • Major
    • Resolution: Fixed
    • 0.6.0, 0.7.0, 0.8.0, 0.9.0, 0.10.0, 0.11.0, 0.12.0, 0.13.0, 0.14.0, 1.0.0, 1.1.0
    • 1.2.0
    • CBO, Logical Optimizer
    • None

    Description

      select count(distinct ss_ticket_number) from store_sales;

      can be rewritten as

      select count(1) from (select distinct ss_ticket_number from store_sales) a;

      which may run upto 3x faster

      Attachments

        1. HIVE-10568.1.patch
          36 kB
          Ashutosh Chauhan
        2. HIVE-10568.2.patch
          37 kB
          Ashutosh Chauhan
        3. HIVE-10568.patch
          23 kB
          Ashutosh Chauhan
        4. HIVE-10568.patch
          23 kB
          Ashutosh Chauhan

        Issue Links

        is blocked by

        Bug - A problem which impairs or prevents the functions of the product. HIVE-10607 Combination of ReducesinkDedup + TopN optimization yields incorrect result if there are multiple GBY in reducer

        • Major - Major loss of function.
        • Closed
        is related to

        Sub-task - The sub-task of the issue HIVE-10855 Make HIVE-10568 work with Spark [Spark Branch]

        • Major - Major loss of function.
        • Closed

        Improvement - An improvement or enhancement to an existing feature or task. HIVE-19283 Select count(distinct()) a couple of times stuck in last reducer

        • Major - Major loss of function.
        • Open
        links to

        Web Link RB request

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          People

            ashutoshc Ashutosh Chauhan Assign to me
            mmokhtar Mostafa Mokhtar
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            Dates

              Created:
              Updated:
              Resolved:

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