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  1. Hadoop Map/Reduce
  2. MAPREDUCE-4827

Increase hash quality of HashPartitioner

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Details

    • Improvement
    • Status: Resolved
    • Major
    • Resolution: Won't Fix
    • None
    • None
    • None
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    Description

      hash partitioner is using object.hashCode() for splitting keys into partitions. This results in bad distributions because hashCode() quality is poor.

      These hashCode() functions are sometimes written by hand (very poor quality) and sometimes generated from by commons lang code (poor quality). Applying some transformation on top of hashCode() provides better distribution.

      Attachments

        1. betterhash2.txt
          3 kB
          Radim Kolar
        2. betterhash1.txt
          1 kB
          Radim Kolar

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            Unassigned Unassigned
            hsn Radim Kolar
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            Dates

              Created:
              Updated:
              Resolved: