org.apache.hadoop.hive.ql.lib.LevelOrderWalker Maven / Gradle / Ivy
/**
* 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.hadoop.hive.ql.lib;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Stack;
import org.apache.hadoop.hive.ql.exec.Operator;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.plan.OperatorDesc;
/**
* This is a level-wise walker implementation which dispatches the node in the order
* that the node will only get dispatched after all the parents are dispatched.
*
* Each node will be accessed once while it could be dispatched multiple times.
* e.g., for a lineage generator with operator tree, 2 levels of current node's
* ancestors need to keep in the operator stack.
* FIL(2) FIL(4)
* | |
* RS(3) RS(5)
* \ /
* JOIN(7)
* The join lineage needs to be called twice for JOIN(7) node with different operator
* ancestors.
*/
public class LevelOrderWalker extends DefaultGraphWalker {
// Only specified nodes of these types will be walked.
// Empty set means all the nodes will be walked.
private HashSet> nodeTypes = new HashSet>();
// How many levels of ancestors to keep in the stack during dispatching
private final int numLevels;
/**
* Constructor with keeping all the ancestors in the operator stack during dispatching.
* @param disp Dispatcher to call for each op encountered
*/
public LevelOrderWalker(Dispatcher disp) {
super(disp);
this.numLevels = Integer.MAX_VALUE;
}
/**
* Constructor with specified number of ancestor levels to keep in the operator
* stack during dispatching.
* @param disp Dispatcher to call for each op encountered
* @param numLevels Number of ancestor levels
*/
public LevelOrderWalker(Dispatcher disp, int numLevels) {
super(disp);
this.numLevels = numLevels;
}
@SuppressWarnings("unchecked")
public void setNodeTypes(Class ...nodeTypes) {
this.nodeTypes.addAll(Arrays.asList(nodeTypes));
}
/**
* starting point for walking.
*
* @throws SemanticException
*/
@SuppressWarnings("unchecked")
@Override
public void startWalking(Collection startNodes,
HashMap nodeOutput) throws SemanticException {
toWalk.addAll(startNodes);
// Starting from the startNodes, add the children whose parents have been
// included in the list.
HashSet addedNodes = new HashSet();
for (Node node : startNodes) {
addedNodes.add(node);
}
int index = 0;
while(index < toWalk.size()) {
if (toWalk.get(index).getChildren() != null) {
for(Node child : toWalk.get(index).getChildren()) {
Operator childOP =
(Operator) child;
if (!addedNodes.contains(child) &&
(childOP.getParentOperators() == null ||
addedNodes.containsAll(childOP.getParentOperators()))) {
toWalk.add(child);
addedNodes.add(child);
}
}
}
++index;
}
for(Node nd : toWalk) {
if (!nodeTypes.isEmpty() && !nodeTypes.contains(nd.getClass())) {
continue;
}
opStack.clear();
opStack.push(nd);
walk(nd, 0, opStack);
if (nodeOutput != null && getDispatchedList().contains(nd)) {
nodeOutput.put(nd, retMap.get(nd));
}
}
}
/**
* Enumerate numLevels of ancestors by putting them in the stack and dispatch
* the current node.
* @param nd current operator in the ancestor tree
* @param level how many level of ancestors included in the stack
* @param stack operator stack
* @throws SemanticException
*/
@SuppressWarnings("unchecked")
private void walk(Node nd, int level, Stack stack) throws SemanticException {
List> parents =
((Operator)nd).getParentOperators();
if (level >= numLevels || parents == null || parents.isEmpty()) {
dispatch(stack.peek(), stack);
return;
}
for(Node parent : parents) {
stack.add(0, parent);
walk(parent, level+1, stack);
stack.remove(0);
}
}
}