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From "Radim Kolar (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MAPREDUCE-4827) Increase hash quality of HashPartitioner
Date Wed, 28 Nov 2012 17:03:01 GMT
Radim Kolar created MAPREDUCE-4827:

             Summary: Increase hash quality of HashPartitioner
                 Key: MAPREDUCE-4827
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4827
             Project: Hadoop Map/Reduce
          Issue Type: Improvement
            Reporter: Radim Kolar

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.

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