/*
 * 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.pig.backend.hadoop.executionengine.mapReduceLayer;

import org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.plans.MROpPlanVisitor;
import org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.plans.MROperPlan;
import org.apache.pig.backend.hadoop.executionengine.util.AccumulatorOptimizerUtil;
import org.apache.pig.impl.plan.DepthFirstWalker;
import org.apache.pig.impl.plan.VisitorException;

/**
 * A visitor to optimize plans that determines if a reduce plan can run in
 * accumulative mode.
 */
public class AccumulatorOptimizer extends MROpPlanVisitor {

    public AccumulatorOptimizer(MROperPlan plan) {
        super(plan, new DepthFirstWalker<MapReduceOper, MROperPlan>(plan));
    }

    public void visitMROp(MapReduceOper mr) throws VisitorException {
        AccumulatorOptimizerUtil.addAccumulator(mr.reducePlan, mr.reducePlan.getRoots());
    }
}
