[jira] [Created] (FLINK-925) Support KeySelector function returning Tuples

[Shang Yuanchun (Jira)]

Fabian Hueske created FLINK-925:
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             Summary: Support KeySelector function returning Tuples
                 Key: FLINK-925
                 URL: https://issues.apache.org/jira/browse/FLINK-925
             Project: Flink
          Issue Type: Improvement
    Affects Versions: 0.6-incubating
            Reporter: Fabian Hueske
            Priority: Minor


KeySelector functions are used to extract keys on which DataSets can be grouped or joined.
Currently, the keys types returned by KeySelector function are restricted to be comparable. However, Flinks Tuple data types are not comparable (because this depends on the types of its fields) which makes grouping and joining on composite keys difficult.

We should change the signature of the groupBy(), join(), and coGroup() methods to allow also non-comparable keys as return types of a KeySelector function.
Instead we will check at optimization time whether the returned type is comparable (which is true for tuples if all elements are comparable).



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