org.apache.drill.common.graph.AdjacencyList.java Source code

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Here is the source code for org.apache.drill.common.graph.AdjacencyList.java

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/**
 * 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.drill.common.graph;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Multimaps;

class AdjacencyList<V extends GraphValue<V>> {
    private Set<Node> allNodes = new HashSet<Node>();
    private ListMultimap<Node, Edge<Node>> adjacencies = ArrayListMultimap.create();

    void addEdge(Node source, Node target, int weight) {
        adjacencies.put(source, new Edge<Node>(source, target, weight));
        allNodes.add(source);
        allNodes.add(target);
    }

    void clearVisited() {
        for (Edge<Node> e : adjacencies.values()) {
            e.from.visited = false;
            e.to.visited = false;
        }
    }

    Node getNewNode(V value) {
        return new Node(value);
    }

    public List<Edge<Node>> getAdjacent(AdjacencyList<V>.Node source) {
        return adjacencies.get(source);
    }

    public void printEdges() {
        for (Edge<Node> e : adjacencies.values()) {
            System.out.println(e.from.index + " -> " + e.to.index);
        }
    }

    public AdjacencyList<V> getReversedList() {
        AdjacencyList<V> newlist = new AdjacencyList<V>();
        for (Edge<Node> e : adjacencies.values()) {
            newlist.addEdge(e.to, e.from, e.weight);
        }
        return newlist;
    }

    public Set<Node> getNodeSet() {
        return adjacencies.keySet();
    }

    Collection<Node> getInternalLeafNodes() {
        // we have to use the allNodes list as otherwise destination only nodes won't be found.
        List<Node> nodes = new LinkedList<Node>(allNodes);

        for (Iterator<Node> i = nodes.iterator(); i.hasNext();) {
            final Node n = i.next();

            // remove any nodes that have one or more outbound edges.
            List<Edge<Node>> adjList = this.getAdjacent(n);
            if (adjList != null && !adjList.isEmpty()) {
                i.remove();
            }

        }
        return nodes;
    }

    /**
     * Get a list of nodes that have no outbound edges.
     *
     * @return
     */
    public Collection<V> getLeafNodes() {
        return convert(getInternalLeafNodes());
    }

    Collection<Node> getInternalRootNodes() {
        Set<Node> nodes = new HashSet<Node>(getNodeSet());
        for (Edge<Node> e : adjacencies.values()) {
            nodes.remove(e.to);
        }
        return nodes;
    }

    /**
     * Get a list of all nodes that have no incoming edges.
     *
     * @return
     */
    public List<V> getRootNodes() {
        return convert(getInternalRootNodes());
    }

    public Collection<Edge<Node>> getAllEdges() {
        return adjacencies.values();
    }

    public void fix(boolean requireDirected) {
        adjacencies = Multimaps.unmodifiableListMultimap(adjacencies);
        allNodes = Collections.unmodifiableSet(allNodes);

        if (requireDirected) {
            List<List<Node>> cyclicReferences = GraphAlgos.checkDirected(this);
            if (cyclicReferences.size() > 0) {
                throw new IllegalArgumentException(
                        "A logical plan must be a valid DAG.  You have cyclic references in your graph.  "
                                + cyclicReferences);
            }
        }
    }

    List<V> convert(Collection<Node> nodes) {
        List<V> out = new ArrayList<V>(nodes.size());
        for (Node o : nodes) {
            out.add(o.getNodeValue());
        }
        return out;
    }

    class Node implements Comparable<Node> {
        final V nodeValue;
        boolean visited = false; // used for Kosaraju's algorithm and Edmonds's
                                 // algorithm
        int lowlink = -1; // used for Tarjan's algorithm
        int index = -1; // used for Tarjan's algorithm

        public Node(final V operator) {
            if (operator == null) {
                throw new IllegalArgumentException("Operator node was null.");
            }
            this.nodeValue = operator;
        }

        public int compareTo(final Node argNode) {
            // just do an identity compare since elsewhere you should ensure that only one node exists for each nodeValue.
            return argNode == this ? 0 : -1;
        }

        @Override
        public int hashCode() {
            return nodeValue.hashCode();
        }

        public V getNodeValue() {
            return nodeValue;
        }

        @Override
        public String toString() {
            return "Node [val=" + nodeValue + "]";
        }

    }

    public static <V extends GraphValue<V>> AdjacencyList<V> newInstance(Collection<V> nodes) {
        AdjacencyList<V> list = new AdjacencyList<V>();
        AdjacencyListBuilder<V> builder = new AdjacencyListBuilder<V>(list);
        for (V v : nodes) {
            v.accept(builder);
        }
        return builder.getAdjacencyList();
    }

}