[FLINK-6789] [optimizer] Remove duplicated test utility reducer in optimizer

This closes #4216.

flink-optimizer/src/test/java/org/apache/flink/optimizer/custompartition/GroupingKeySelectorTranslationTest.java

@@ -34,7 +34,7 @@ import org.apache.flink.api.java.tuple.Tuple3;
 import org.apache.flink.optimizer.plan.OptimizedPlan;
 import org.apache.flink.optimizer.plan.SingleInputPlanNode;
 import org.apache.flink.optimizer.plan.SinkPlanNode;
-import org.apache.flink.optimizer.testfunctions.DummyReducer;
+import org.apache.flink.optimizer.testfunctions.SelectOneReducer;
 import org.apache.flink.optimizer.testfunctions.IdentityGroupReducerCombinable;
 import org.apache.flink.optimizer.util.CompilerTestBase;
 import org.apache.flink.runtime.operators.shipping.ShipStrategyType;
@@ -53,7 +53,7 @@ public class GroupingKeySelectorTranslationTest extends CompilerTestBase {
 			
 			data.groupBy(new TestKeySelector<Tuple2<Integer,Integer>>())
 				.withPartitioner(new TestPartitionerInt())
-				.reduce(new DummyReducer<Tuple2<Integer,Integer>>())
+				.reduce(new SelectOneReducer<Tuple2<Integer,Integer>>())
 				.output(new DiscardingOutputFormat<Tuple2<Integer, Integer>>());
 			
 			Plan p = env.createProgramPlan();

flink-optimizer/src/test/java/org/apache/flink/optimizer/custompartition/GroupingPojoTranslationTest.java

@@ -30,7 +30,7 @@ import org.apache.flink.api.java.io.DiscardingOutputFormat;
 import org.apache.flink.optimizer.plan.OptimizedPlan;
 import org.apache.flink.optimizer.plan.SingleInputPlanNode;
 import org.apache.flink.optimizer.plan.SinkPlanNode;
-import org.apache.flink.optimizer.testfunctions.DummyReducer;
+import org.apache.flink.optimizer.testfunctions.SelectOneReducer;
 import org.apache.flink.optimizer.testfunctions.IdentityGroupReducerCombinable;
 import org.apache.flink.optimizer.util.CompilerTestBase;
 import org.apache.flink.runtime.operators.shipping.ShipStrategyType;
@@ -48,7 +48,7 @@ public class GroupingPojoTranslationTest extends CompilerTestBase {
 					.rebalance().setParallelism(4);
 
 			data.groupBy("a").withPartitioner(new TestPartitionerInt())
-					.reduce(new DummyReducer<Pojo2>())
+					.reduce(new SelectOneReducer<Pojo2>())
 					.output(new DiscardingOutputFormat<Pojo2>());
 
 			Plan p = env.createProgramPlan();
@@ -255,4 +255,4 @@ public class GroupingPojoTranslationTest extends CompilerTestBase {
 			return 0;
 		}
 	}
-}
+}
\ No newline at end of file

flink-optimizer/src/test/java/org/apache/flink/optimizer/custompartition/GroupingTupleTranslationTest.java

@@ -33,7 +33,7 @@ import org.apache.flink.api.java.tuple.Tuple4;
 import org.apache.flink.optimizer.plan.OptimizedPlan;
 import org.apache.flink.optimizer.plan.SingleInputPlanNode;
 import org.apache.flink.optimizer.plan.SinkPlanNode;
-import org.apache.flink.optimizer.testfunctions.DummyReducer;
+import org.apache.flink.optimizer.testfunctions.SelectOneReducer;
 import org.apache.flink.optimizer.testfunctions.IdentityGroupReducerCombinable;
 import org.apache.flink.optimizer.util.CompilerTestBase;
 import org.apache.flink.runtime.operators.shipping.ShipStrategyType;
@@ -80,7 +80,7 @@ public class GroupingTupleTranslationTest extends CompilerTestBase {
 					.rebalance().setParallelism(4);
 			
 			data.groupBy(0).withPartitioner(new TestPartitionerInt())
-				.reduce(new DummyReducer<Tuple2<Integer,Integer>>())
+				.reduce(new SelectOneReducer<Tuple2<Integer,Integer>>())
 				.output(new DiscardingOutputFormat<Tuple2<Integer, Integer>>());
 			
 			Plan p = env.createProgramPlan();

flink-optimizer/src/test/java/org/apache/flink/optimizer/testfunctions/DummyReducer.java

-/*
- * 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.optimizer.testfunctions;
-
-import org.apache.flink.api.common.functions.RichReduceFunction;
-
-public class DummyReducer<T> extends RichReduceFunction<T> {
-
-	private static final long serialVersionUID = 1L;
-
-	@Override
-	public T reduce(T a, T b) {
-		return a;
-	}
-}