org.apache.hadoop.hive.ql.lib.CostLessRuleDispatcher 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
* 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
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*/
package org.apache.hadoop.hive.ql.lib;
import java.util.Stack;
import com.google.common.collect.SetMultimap;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.parse.ASTNode;
/**
* Dispatches calls to relevant method in processor. The user registers various
* rules with the dispatcher, and the processor corresponding to the type of node
*/
public class CostLessRuleDispatcher implements SemanticDispatcher {
private final SetMultimap procRules;
private final NodeProcessorCtx procCtx;
private final SemanticNodeProcessor defaultProc;
/**
* Constructor.
*
* @param defaultProc default processor to be fired if no rule matches
* @param rules Map mapping the node's type to processor
* @param procCtx operator processor context, which is opaque to the dispatcher
*/
public CostLessRuleDispatcher(SemanticNodeProcessor defaultProc, SetMultimap rules,
NodeProcessorCtx procCtx) {
this.defaultProc = defaultProc;
procRules = rules;
this.procCtx = procCtx;
}
/**
* Dispatcher function.
*
* @param nd operator to process
* @param ndStack the operators encountered so far
* @throws SemanticException
*/
@Override public Object dispatch(Node nd, Stack ndStack, Object... nodeOutputs)
throws SemanticException {
int nodeType = ((ASTNode) nd).getType();
SemanticNodeProcessor processor = this.defaultProc;
if (this.procRules.containsKey(nodeType)) {
processor = this.procRules.get(((ASTNode) nd).getType()).iterator().next();
}
return processor.process(nd, ndStack, procCtx, nodeOutputs);
}
}