org.apache.flink.optimizer.dag.MapNode Maven / Gradle / Ivy

/*
 * 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.dag;

import java.util.Collections;
import java.util.List;

import org.apache.flink.api.common.operators.SingleInputOperator;
import org.apache.flink.optimizer.DataStatistics;
import org.apache.flink.optimizer.operators.MapDescriptor;
import org.apache.flink.optimizer.operators.OperatorDescriptorSingle;

/**
 * The optimizer's internal representation of a Map operator node.
 */
public class MapNode extends SingleInputNode {
	
	private final List possibleProperties;
	
	/**
	 * Creates a new MapNode for the given operator.
	 * 
	 * @param operator The map operator.
	 */
	public MapNode(SingleInputOperator operator) {
		super(operator);
		
		this.possibleProperties = Collections.singletonList(new MapDescriptor());
	}

	@Override
	public String getOperatorName() {
		return "Map";
	}

	@Override
	protected List getPossibleProperties() {
		return this.possibleProperties;
	}

	/**
	 * Computes the estimates for the Map 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) {
		this.estimatedNumRecords = getPredecessorNode().getEstimatedNumRecords();
	}
}