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  1. Pig
  2. PIG-4885

Turn off union optimizer if there is PARALLEL clause in union in Tez

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    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 0.16.0
    • Component/s: None
    • Labels:
      None
    • Hadoop Flags:
      Reviewed

      Description

      In mapreduce, if PARALLEL clause was specified on UNION it was ignored as it was a map operation and split size was used. In Tez, when union optimizer is turned off it is a reduce side operation and we should let user control parallelism instead of relying on just auto-parallelism. This is specifically useful when user needs to control the number of output files.

      data = UNION A, B, C, D, E, F, G, H, I, J;
      store data;

      In the above case instead of manually controlling parallelism of A to J aliases to achieve desired parallelism the UNION clause can specify the desired parallelism using PARALLEL. i.e

      data = UNION A, B, C, D, E, F, G, H, I, J PARALLEL 50;

      This only works today if we set pig.tez.opt.union=false. We should automatically and selectively turn off union optimization for those unions that have PARALLEL clause.

        Attachments

        1. PIG-4885-1.patch
          10 kB
          Rohini Palaniswamy

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            • Assignee:
              rohini Rohini Palaniswamy
              Reporter:
              rohini Rohini Palaniswamy
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              Dates

              • Created:
                Updated:
                Resolved: