Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/incubator-flink/pull/42#discussion_r14509146
--- Diff:
stratosphere-compiler/src/main/java/eu/stratosphere/compiler/dag/MapPartitionNode.java
---
@@ -0,0 +1,56 @@
+/***********************************************************************************************************************
+ * Copyright (C) 2010-2013 by the Stratosphere project
(http://stratosphere.eu)
+ *
+ * Licensed 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 eu.stratosphere.compiler.dag;
+
+import java.util.Collections;
+import java.util.List;
+
+import eu.stratosphere.api.common.operators.SingleInputOperator;
+import eu.stratosphere.compiler.DataStatistics;
+import eu.stratosphere.compiler.operators.MapPartitionDescriptor;
+import eu.stratosphere.compiler.operators.OperatorDescriptorSingle;
+
+/**
+ * The optimizer's internal representation of a <i>MapPartition</i>
operator node.
+ */
+public class MapPartitionNode extends SingleInputNode {
+
+ /**
+ * Creates a new MapNode for the given contract.
+ *
+ * @param operator The map partition contract object.
+ */
+ public MapPartitionNode(SingleInputOperator<?, ?, ?> operator) {
+ super(operator);
+ }
+
+ @Override
+ public String getName() {
+ return "MapPartition";
+ }
+
+ @Override
+ protected List<OperatorDescriptorSingle> getPossibleProperties() {
+ return Collections.<OperatorDescriptorSingle>singletonList(new
MapPartitionDescriptor());
+ }
+
+ /**
+ * Computes the estimates for the MapPartition operator.
+ * We assume that by default, Map takes one value and transforms it
into another value.
+ * The cardinality consequently stays the same.
+ */
+ @Override
+ protected void computeOperatorSpecificDefaultEstimates(DataStatistics
statistics) {
+ }
--- End diff --
I agree with fabian. Let's leave this empty, because there are really no
good assumptions to make for this function.
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