/*
 * 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.SemanticProperties;
import org.apache.flink.api.common.operators.SingleInputOperator;
import org.apache.flink.optimizer.DataStatistics;
import org.apache.flink.optimizer.operators.MapPartitionDescriptor;
import org.apache.flink.optimizer.operators.OperatorDescriptorSingle;
import org.apache.flink.api.common.operators.SingleInputSemanticProperties;
import org.apache.flink.api.common.operators.util.FieldSet;

/**
 * The optimizer's internal representation of a <i>MapPartition</i> operator node.
 */
public class MapPartitionNode extends SingleInputNode {
	
	private final List<OperatorDescriptorSingle> possibleProperties;
	
	/**
	 * Creates a new MapNode for the given contract.
	 * 
	 * @param operator The map partition contract object.
	 */
	public MapPartitionNode(SingleInputOperator<?, ?, ?> operator) {
		super(operator);
		
		this.possibleProperties = Collections.<OperatorDescriptorSingle>singletonList(new MapPartitionDescriptor());
	}

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

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

	@Override
	protected SemanticProperties getSemanticPropertiesForLocalPropertyFiltering() {

		// Local properties for MapPartition may not be preserved.
		SingleInputSemanticProperties origProps =
				((SingleInputOperator<?,?,?>) getOperator()).getSemanticProperties();
		SingleInputSemanticProperties filteredProps = new SingleInputSemanticProperties();
		FieldSet readSet = origProps.getReadFields(0);
		if(readSet != null) {
			filteredProps.addReadFields(readSet);
		}

		return filteredProps;
	}

	/**
	 * 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) {
		// we really cannot make any estimates here
	}
}