org.apache.hadoop.hive.ql.lib.ExpressionWalker Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
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*/
package org.apache.hadoop.hive.ql.lib;
import org.apache.hadoop.hive.ql.parse.ASTNode;
import org.apache.hadoop.hive.ql.parse.HiveParser;
import org.apache.hadoop.hive.ql.parse.SemanticException;
public class ExpressionWalker extends DefaultGraphWalker {
/**
* Constructor.
*
* @param disp
* dispatcher to call for each op encountered
*/
public ExpressionWalker(Dispatcher disp) {
super(disp);
}
/**
* We should bypass subquery since we have already processed and created logical plan
* (in genLogicalPlan) for subquery at this point.
* SubQueryExprProcessor will use generated plan and creates appropriate ExprNodeSubQueryDesc.
*/
private boolean shouldByPass(Node childNode, Node parentNode) {
if(parentNode instanceof ASTNode
&& ((ASTNode)parentNode).getType() == HiveParser.TOK_SUBQUERY_EXPR) {
ASTNode parentOp = (ASTNode)parentNode;
//subquery either in WHERE IN form OR WHERE EXISTS form
//in first case LHS should not be bypassed
assert(parentOp.getChildCount() == 2 || parentOp.getChildCount()==3);
if(parentOp.getChildCount() == 3 && (ASTNode)childNode == parentOp.getChild(2)) {
return false;
}
return true;
}
return false;
}
/**
* walk the current operator and its descendants.
*
* @param nd
* current operator in the graph
* @throws SemanticException
*/
protected void walk(Node nd) throws SemanticException {
// Push the node in the stack
opStack.push(nd);
// While there are still nodes to dispatch...
while (!opStack.empty()) {
Node node = opStack.peek();
if (node.getChildren() == null ||
getDispatchedList().containsAll(node.getChildren())) {
// Dispatch current node
if (!getDispatchedList().contains(node)) {
dispatch(node, opStack);
opQueue.add(node);
}
opStack.pop();
continue;
}
// Add a single child and restart the loop
for (Node childNode : node.getChildren()) {
if (!getDispatchedList().contains(childNode)) {
if(shouldByPass(childNode, node)) {
retMap.put(childNode, null);
} else {
opStack.push(childNode);
}
break;
}
}
} // end while
}
}