org.apache.hadoop.hive.ql.lib.RuleExactMatch Maven / Gradle / Ivy
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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.hadoop.hive.ql.lib;
import java.util.Stack;
import org.apache.hadoop.hive.ql.parse.SemanticException;
/**
* Implentation of the Rule interface for Nodes Used in Node dispatching to dispatch
* process/visitor functions for Nodes. The cost method returns 1 if there is an exact
* match between the expression and the stack, otherwise -1.
*/
public class RuleExactMatch implements Rule {
private final String ruleName;
private final String pattern;
/**
* The rule specified as operator names separated by % symbols, the left side represents the
* bottom of the stack.
*
* E.g. TS%FIL%RS -> means
* TableScan Node followed by Filter followed by ReduceSink in the tree, or, in terms of the
* stack, ReduceSink on top followed by Filter followed by TableScan
*
* @param ruleName
* name of the rule
* @param regExp
* string specification of the rule
**/
public RuleExactMatch(String ruleName, String pattern) {
this.ruleName = ruleName;
this.pattern = pattern;
}
/**
* This function returns the cost of the rule for the specified stack. Returns 1 if there is
* an exact match with the entire stack, otherwise -1
*
* If any proper substack of the stack matches it will return -1. It only returns 1 if the
* entire stack matches the rule exactly.
*
* @param stack
* Node stack encountered so far
* @return cost of the function
* @throws SemanticException
*/
public int cost(Stack stack) throws SemanticException {
int numElems = (stack != null ? stack.size() : 0);
String name = new String();
for (int pos = numElems - 1; pos >= 0; pos--) {
name = stack.get(pos).getName() + "%" + name;
}
if (pattern.equals(name)) {
return 1;
}
return -1;
}
/**
* @return the name of the Node
**/
public String getName() {
return ruleName;
}
}