| /* |
| * 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.ArrayList; |
| 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; |
| |
| /** |
| * Visit a plan in the reverse of the dependency order. That is, every node |
| * after every node that depends on it is visited. Thus this is equivalent to |
| * doing a reverse topilogical sort on the graph and then visiting it in order. |
| */ |
| public class ReverseDependencyOrderWalker extends PlanWalker { |
| |
| public ReverseDependencyOrderWalker(OperatorPlan plan) { |
| super(plan); |
| } |
| |
| @Override |
| public PlanWalker spawnChildWalker(OperatorPlan plan) { |
| return new ReverseDependencyOrderWalker(plan); |
| } |
| |
| /** |
| * Begin traversing the graph. |
| * @param visitor Visitor this walker is being used by. |
| * @throws VisitorException if an error is encountered while walking. |
| */ |
| @Override |
| public void walk(PlanVisitor visitor) throws FrontendException { |
| // This is highly inefficient, but our graphs are small so it should be okay. |
| // The algorithm works by starting at any node in the graph, finding it's |
| // successors and calling itself for each of those successors. When it |
| // finds a node that has no unfinished successors it puts that node in the |
| // list. It then unwinds itself putting each of the other nodes in the list. |
| // It keeps track of what nodes it's seen as it goes so it doesn't put any |
| // nodes in the graph twice. |
| |
| List<Operator> fifo = new ArrayList<Operator>(); |
| Set<Operator> seen = new HashSet<Operator>(); |
| List<Operator> roots = plan.getSources(); |
| if (roots == null) return; |
| for (Operator op : roots) { |
| doAllSuccessors(op, seen, fifo); |
| } |
| |
| for (Operator op: fifo) { |
| op.accept(visitor); |
| } |
| } |
| |
| protected void doAllSuccessors(Operator node, |
| Set<Operator> seen, |
| Collection<Operator> fifo) throws FrontendException { |
| if (!seen.contains(node)) { |
| // We haven't seen this one before. |
| Collection<Operator> succs = Utils.mergeCollection(plan.getSuccessors(node), plan.getSoftLinkSuccessors(node)); |
| if (succs != null && succs.size() > 0) { |
| // Do all our successors before ourself |
| for (Operator op : succs) { |
| doAllSuccessors(op, seen, fifo); |
| } |
| } |
| // Now do ourself |
| seen.add(node); |
| fifo.add(node); |
| } |
| } |
| } |