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  1. Hadoop Common
  2. HADOOP-3226

Run combiner when merging spills from map output

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    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 0.18.0
    • Component/s: None
    • Labels:
      None
    • Hadoop Flags:
      Incompatible change, Reviewed
    • Release Note:
      Hide
      Changed policy for running combiner. The combiner may be run multiple times as the map's output is sorted and merged. Additionally, it may be run on the reduce side as data is merged. The old semantics are available in Hadoop 0.18 if the user calls:
      job.setCombineOnlyOnce(true);
      Show
      Changed policy for running combiner. The combiner may be run multiple times as the map's output is sorted and merged. Additionally, it may be run on the reduce side as data is merged. The old semantics are available in Hadoop 0.18 if the user calls: job.setCombineOnlyOnce(true);

      Description

      When merging spills from the map, running the combiner should further diminish the volume of data we send to the reduce.

        Attachments

        1. 3226-3.patch
          13 kB
          Christopher Douglas
        2. 3226-2.patch
          15 kB
          Christopher Douglas
        3. 3226-1.patch
          15 kB
          Christopher Douglas
        4. 3226-0.patch
          2 kB
          Christopher Douglas

          Activity

            People

            • Assignee:
              cdouglas Christopher Douglas
              Reporter:
              cdouglas Christopher Douglas
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              Dates

              • Created:
                Updated:
                Resolved: