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From: markus-h <git@git.apache.org>
To: dev@flink.incubator.apache.org
Reply-To: dev@flink.incubator.apache.org
References: <git-pr-42-incubator-flink@git.apache.org>
In-Reply-To: <git-pr-42-incubator-flink@git.apache.org>
Subject: [GitHub] incubator-flink pull request: New operator map partition
 function
Content-Type: text/plain
Message-Id: <20140625145124.F04EB93A814@tyr.zones.apache.org>
Date: Wed, 25 Jun 2014 14:51:24 +0000 (UTC)

Github user markus-h commented on a diff in the pull request:

    https://github.com/apache/incubator-flink/pull/42#discussion_r14190037
  
    --- 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 --
    
    Why did you leave this method empty?
    I think it should be something similar to the regular map:
    this.estimatedNumRecords = getPredecessorNode().getEstimatedNumRecords();


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