Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/1704#discussion_r55993657
--- Diff:
flink-scala/src/main/scala/org/apache/flink/api/scala/extensions/acceptPartialFunctions/OnGroupedDataSet.scala
---
@@ -0,0 +1,75 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.flink.api.scala.extensions.acceptPartialFunctions
+
+import org.apache.flink.api.common.operators.Order
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.api.scala.{DataSet, GroupedDataSet}
+
+import scala.reflect.ClassTag
+
+class OnGroupedDataSet[T: ClassTag](ds: GroupedDataSet[T]) {
+
+ /**
+ * Sorts a group using a sorting function `fun` and an `Order`
+ *
+ * @param fun The sorting function, defining the sorting key
+ * @param order The ordering strategy (ascending, descending, etc.)
+ * @tparam K The key type
+ * @return A data set sorted group-wise
+ */
+ def sortGroupWith[K: TypeInformation](order: Order)(fun: T => K):
GroupedDataSet[T] =
+ ds.sortGroup(fun, order)
+
+ /**
+ * Reduces the whole data set with a reducer `fun`
+ *
+ * @param fun The reducing function
+ * @return A reduced data set of Ts
+ */
+ def reduceWith(fun: (T, T) => T): DataSet[T] =
+ ds.reduce(fun)
+
+ /**
+ * Reduces the data set group-wise with a reducer `fun`
+ *
+ * @param fun The reducing function
+ * @tparam R The type of the items in the resulting data set
+ * @return A data set of Rs reduced group-wise
+ */
+ def reduceGroupWith[R: TypeInformation: ClassTag](fun: Seq[T] => R):
DataSet[R] =
+ ds.reduceGroup {
+ (it, out) =>
+ out.collect(fun(it.to[Seq]))
--- End diff --
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