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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