Github user ggevay commented on a diff in the pull request:
https://github.com/apache/flink/pull/1517#discussion_r65219886
--- Diff:
flink-scala/src/main/scala/org/apache/flink/api/scala/GroupedDataSet.scala ---
@@ -282,27 +283,57 @@ class GroupedDataSet[T: ClassTag](
}
/**
- * Creates a new [[DataSet]] by merging the elements of each group
(elements with the same key)
- * using an associative reduce function.
- */
+ * Creates a new [[DataSet]] by merging the elements of each group
(elements with the same key)
+ * using an associative reduce function.
+ */
def reduce(fun: (T, T) => T): DataSet[T] = {
+ reduce(getCallLocationName(), fun, CombineHint.OPTIMIZER_CHOOSES)
+ }
+
+ /**
+ * Special [[reduce]] operation for explicitly telling the system what
strategy to use for the
+ * combine phase.
+ * If null is given as the strategy, then the optimizer will pick the
strategy.
+ */
+ def reduce(fun: (T, T) => T, strategy: CombineHint): DataSet[T] = {
--- End diff --
> Would it be OK if I added optional arguments instead of the overloads
like this?
Oops, this doesn't work. I'm getting
```
Error:(45, 7) in class GroupedDataSet, multiple overloaded alternatives of
reduce define default arguments
```
An alternative solution would be to instead of just wrapping in a Scala
`DataSet`, create a Scala class that wraps `ReduceOperator`, has the same
`setCombineHint` method, and inherits from the Scala `DataSet`.
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