Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/1856#discussion_r67049570
--- Diff:
flink-scala/src/main/scala/org/apache/flink/api/scala/GroupedDataSet.scala ---
@@ -356,6 +358,44 @@ class GroupedDataSet[T: ClassTag](
}
/**
+ * Applies a special case of a reduce transformation (maxBy) on a
grouped {@link DataSet}.<br>
+ * The transformation consecutively calls a {@link ReduceFunction}
+ * until only a single element remains which is the result of the
transformation.
+ * A ReduceFunction combines two elements into one new element of the
same type.
+ *
+ * @param fields Keys taken into account for finding the minimum.
+ * @return A { @link ReduceOperator} representing the minimum.
+ */
+ def maxBy(fields: Array[Int]) : ReduceOperator[T] = {
--- End diff --
Do not use `Array[Int]` as parameter. This is clumsy and not consistent
with the remaining API. Use `fields: Int*` instead. `fields.toArray` converts
to an Array.
This applies to all `maxBy`, `minBy` functions.
Do not use `ReduceOperator` as return type. This is a Java DataSet API
class and must not be mix with the Scala API! Use `DataSet[T]` instead.
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