org.apache.hadoop.hive.ql.lib.ExpressionWalker Maven / Gradle / Ivy
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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
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*/
package org.apache.hadoop.hive.ql.lib;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import java.util.ArrayDeque;
import java.util.Deque;
/**
* class for traversing tree
* This class assumes that the given node represents TREE and not GRAPH
* i.e. there is only single path to reach a node
*/
public class ExpressionWalker extends DefaultGraphWalker{
/**
* Constructor.
*
* @param disp
* dispatcher to call for each op encountered
*/
public ExpressionWalker(SemanticDispatcher disp) {
super(disp);
}
private static class NodeLabeled {
final private Node nd;
private int currChildIdx;
NodeLabeled(Node nd) {
this.nd = nd;
this.currChildIdx = -1;
}
public void incrementChildIdx() {
this.currChildIdx++;
}
public int getCurrChildIdx() {
return this.currChildIdx;
}
public Node getNd() {
return this.nd;
}
}
protected boolean shouldByPass(Node childNode, Node parentNode) {
return false;
}
/**
* walk the current operator and its descendants.
*
* @param nd
* current operator in the tree
* @throws SemanticException
*/
protected void walk(Node nd) throws SemanticException {
Deque traversalStack = new ArrayDeque<>();
traversalStack.push(new NodeLabeled(nd));
opStack.push(nd);
while(!traversalStack.isEmpty()) {
NodeLabeled currLabeledNode = traversalStack.peek();
Node currNode = currLabeledNode.getNd();
int currIdx = currLabeledNode.getCurrChildIdx();
if(currNode.getChildren() != null && currNode.getChildren().size() > currIdx + 1) {
Node nextChild = currNode.getChildren().get(currIdx+1);
//check if this node should be skipped and not dispatched
if(shouldByPass(nextChild, currNode)) {
retMap.put(nextChild, null);
currLabeledNode.incrementChildIdx();
continue;
}
traversalStack.push(new NodeLabeled(nextChild));
opStack.push(nextChild);
currLabeledNode.incrementChildIdx();
} else {
// dispatch the node
dispatch(currNode, opStack);
opQueue.add(currNode);
opStack.pop();
traversalStack.pop();
}
}
}
}