[jira] [Created] (HIVE-5839) BytesRefArrayWritable compareTo violates contract

["Ian Robertson (JIRA)" <ji...@apache.org>]

Ian Robertson created HIVE-5839:
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             Summary: BytesRefArrayWritable compareTo violates contract
                 Key: HIVE-5839
                 URL: https://issues.apache.org/jira/browse/HIVE-5839
             Project: Hive
          Issue Type: Bug
          Components: Serializers/Deserializers
    Affects Versions: 0.11.0
            Reporter: Ian Robertson


BytesRefArrayWritable's compareTo violates the compareTo contract from java.lang.Object. Specifically:

    The implementor must ensure sgn(x.compareTo(y)) == -sgn(y.compareTo(x)) for all x and y.

The compareTo implementation on BytesRefArrayWritable does a proper comparison of the sizes of the two instances. However, if the sizes are the same, it proceeds to do a check if both array's have the same constant. If not, it returns 1. This means that if x and y are two BytesRefArrayWritable instances with the same size, but different contents, then x.compareTo(y) == 1 and y.compareTo(x) == 1.

Additionally, the comparison of contents is order agnostic. This seems wrong, since order of entries should matter. It is also very inefficient, running at O(n^2), where n is the number of entries.



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