/*
 * 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.wayang.core.optimizer.cardinality;

import org.apache.wayang.core.optimizer.OptimizationContext;
import org.apache.wayang.core.plan.wayangplan.InputSlot;
import org.apache.wayang.core.plan.wayangplan.Operator;
import org.apache.wayang.core.plan.wayangplan.OutputSlot;

import java.io.Serializable;

/**
 * Computes {@link CardinalityEstimate}s.
 * <p>To estimate the cardinality of an {@link Operator}'s {@link OutputSlot} given its {@link InputSlot}s' cardinalities
 * is the job of this estimator.</p>
 */
@FunctionalInterface
public interface CardinalityEstimator extends Serializable {

    CardinalityEstimate estimate(OptimizationContext optimizationContext, CardinalityEstimate... inputEstimates);

}
