org.apache.hadoop.hive.ql.lib.Rule 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,
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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 java.util.Stack;
import org.apache.hadoop.hive.ql.parse.SemanticException;
/**
* Rule interface for Operators Used in operator dispatching to dispatch
* process/visitor functions for operators.
*/
public interface Rule {
/**
* @return the cost of the rule - the lower the cost, the better the rule
* matches
* @throws SemanticException
*/
int cost(Stack stack) throws SemanticException;
/**
* @return the name of the rule - may be useful for debugging
*/
String getName();
}