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  1. Hadoop Common
  2. HADOOP-5589

TupleWritable: Lift implicit limit on the number of values that can be stored

    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 0.19.1
    • Fix Version/s: 0.21.0
    • Component/s: None
    • Labels:
      None
    • Hadoop Flags:
      Reviewed

      Description

      TupleWritable uses an instance field of the primitive type, long, which I presume is so that it can quickly determine if a position has been written to in its array of Writables (by using bit-shifting operations on the long field). The problem with this is that it implies that there is a maximum limit of 64 values you can store in a TupleWritable.

      An example of a use-case where I think this would be a problem is if you had two MR jobs with over 64 reduces tasks and you wanted to join the outputs with CompositeInputFormat - this will probably cause unexpected results in the current scheme.

      At the very least, the 64-value limit should be documented in TupleWritable.

        Attachments

        1. HADOOP-5589-4.patch
          14 kB
          Jingkei Ly
        2. HADOOP-5589-4.patch
          14 kB
          Jingkei Ly
        3. HADOOP-5589-3.patch
          10 kB
          Jingkei Ly
        4. HADOOP-5589-2.patch
          10 kB
          Jingkei Ly
        5. HADOOP-5589-1.patch
          9 kB
          Jingkei Ly

          Activity

            People

            • Assignee:
              jly Jingkei Ly
              Reporter:
              jly Jingkei Ly
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              Dates

              • Created:
                Updated:
                Resolved: