| /* |
| * 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.newplan; |
| |
| import java.util.Collection; |
| import java.util.HashSet; |
| import java.util.List; |
| import java.util.Set; |
| |
| import org.apache.pig.impl.logicalLayer.FrontendException; |
| import org.apache.pig.impl.util.Utils; |
| |
| /** |
| * Do a depth first traversal of the graph. |
| */ |
| public class DepthFirstWalker extends PlanWalker { |
| |
| public DepthFirstWalker(OperatorPlan plan) { |
| super(plan); |
| } |
| |
| @Override |
| public PlanWalker spawnChildWalker(OperatorPlan plan) { |
| return new DepthFirstWalker(plan); |
| } |
| |
| /** |
| * Begin traversing the graph. |
| * @param visitor Visitor this walker is being used by. |
| * @throws FrontendException if an error is encountered while walking. |
| */ |
| @Override |
| public void walk(PlanVisitor visitor) throws FrontendException { |
| List<Operator> roots = plan.getSources(); |
| Set<Operator> seen = new HashSet<Operator>(); |
| |
| depthFirst(null, roots, seen, visitor); |
| } |
| |
| private void depthFirst(Operator node, |
| Collection<Operator> successors, |
| Set<Operator> seen, |
| PlanVisitor visitor) throws FrontendException { |
| if (successors == null) return; |
| |
| for (Operator suc : successors) { |
| if (seen.add(suc)) { |
| suc.accept(visitor); |
| Collection<Operator> newSuccessors = Utils.mergeCollection(plan.getSuccessors(suc), plan.getSoftLinkSuccessors(suc)); |
| depthFirst(suc, newSuccessors, seen, visitor); |
| } |
| } |
| } |
| } |