/*
 * 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.SingleInputSemanticProperties;
import org.apache.flink.api.common.operators.base.FilterOperatorBase;
import org.apache.flink.optimizer.DataStatistics;
import org.apache.flink.optimizer.operators.FilterDescriptor;
import org.apache.flink.optimizer.operators.OperatorDescriptorSingle;

/**
 * The optimizer's internal representation of a <i>Filter</i> operator node.
 */
public class FilterNode extends SingleInputNode {
	
	private final List<OperatorDescriptorSingle> possibleProperties;
	
	public FilterNode(FilterOperatorBase<?, ?> operator) {
		super(operator);
		this.possibleProperties = Collections.<OperatorDescriptorSingle>singletonList(new FilterDescriptor());
	}

	@Override
	public FilterOperatorBase<?, ?> getOperator() {
		return (FilterOperatorBase<?, ?>) super.getOperator();
	}

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

	@Override
	public SemanticProperties getSemanticProperties() {
		return new SingleInputSemanticProperties.AllFieldsForwardedProperties();
	}

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

	/**
	 * Computes the estimates for the Filter operator. Since it applies a filter on the data we assume a cardinality
	 * decrease. To give the system a hint at data decrease, we use a default magic number to indicate a 0.5 decrease. 
	 */
	@Override
	protected void computeOperatorSpecificDefaultEstimates(DataStatistics statistics) {
		this.estimatedNumRecords = (long) (getPredecessorNode().getEstimatedNumRecords() * 0.5);
		this.estimatedOutputSize = (long) (getPredecessorNode().getEstimatedOutputSize() * 0.5);
	}
}