Github user chiwanpark commented on the pull request:
https://github.com/apache/flink/pull/905#issuecomment-120913343
Hi, @pp86 Thanks for your contribution.
But I think that using `AutoSelector` is not the best approach to improve
distinct transformation. In Flink, a `KeySelector` converts a `DataSet<O>` to
`DataSet<Tuple2<K, O>>` and uses the first element of the tuple as key. For
atomic types, `AutoSelector` creates `DataSet<Tuple2<V, V>>` which
unnecessarily duplicated data.
I recommend `Keys.ExpressionKeys` when the user call `distinct()` method on
atomic data types.
And It would be better to add the test cases for this changes.
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