org.apache.hadoop.hive.ql.lib.ForwardWalker Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* distributed with this work for additional information
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* 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hive.ql.lib;
import org.apache.hadoop.hive.ql.exec.Operator;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.plan.OperatorDesc;
public class ForwardWalker extends DefaultGraphWalker {
/**
* Constructor.
*
* @param disp
* dispatcher to call for each op encountered
*/
public ForwardWalker(Dispatcher disp) {
super(disp);
}
@SuppressWarnings("unchecked")
protected boolean allParentsDispatched(Node nd) {
Operator op = (Operator) nd;
if (op.getParentOperators() == null) {
return true;
}
for (Node pNode : op.getParentOperators()) {
if (!getDispatchedList().contains(pNode)) {
return false;
}
}
return true;
}
@SuppressWarnings("unchecked")
protected void addAllParents(Node nd) {
Operator op = (Operator) nd;
toWalk.removeAll(op.getParentOperators());
toWalk.addAll(0, op.getParentOperators());
}
/**
* walk the current operator and its descendants.
*
* @param nd
* current operator in the graph
* @throws SemanticException
*/
@Override
protected void walk(Node nd) throws SemanticException {
if (opStack.empty() || nd != opStack.peek()) {
opStack.push(nd);
}
if (allParentsDispatched(nd)) {
// all children are done or no need to walk the children
if (!getDispatchedList().contains(nd)) {
toWalk.addAll(nd.getChildren());
dispatch(nd, opStack);
}
opStack.pop();
return;
}
// add children, self to the front of the queue in that order
toWalk.add(0, nd);
addAllParents(nd);
}
}