org.apache.hadoop.hive.ql.exec.DefaultUDAFEvaluatorResolver 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.exec;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.hive.serde2.typeinfo.TypeInfo;
/**
* The default UDAF Method resolver. This resolver is used for resolving the
* UDAF methods are used for partial and final evaluation given the list of the
* argument types. The getEvalMethod goes through all the evaluate methods and
* returns the one that matches the argument signature or is the closest match.
* Closest match is defined as the one that requires the least number of
* arguments to be converted. In case more than one matches are found, the
* method throws an ambiguous method exception.
*/
public class DefaultUDAFEvaluatorResolver implements UDAFEvaluatorResolver {
/**
* The class of the UDAF.
*/
private final Class udafClass;
/**
* Constructor. This constructor sets the resolver to be used for comparison
* operators. See {@link UDAFEvaluatorResolver}
*/
public DefaultUDAFEvaluatorResolver(Class udafClass) {
this.udafClass = udafClass;
}
/**
* Gets the evaluator class for the UDAF given the parameter types.
*
* @param argClasses
* The list of the parameter types.
*/
public Class getEvaluatorClass(
List argClasses) throws UDFArgumentException {
ArrayList> classList =
new ArrayList>();
// Add all the public member classes that implement an evaluator
for (Class enclClass : udafClass.getClasses()) {
if (UDAFEvaluator.class.isAssignableFrom(enclClass)) {
classList.add((Class) enclClass);
}
}
// Next we locate all the iterate methods for each of these classes.
ArrayList mList = new ArrayList();
ArrayList> cList =
new ArrayList>();
for (Class evaluator : classList) {
for (Method m : evaluator.getMethods()) {
if (m.getName().equalsIgnoreCase("iterate")) {
mList.add(m);
cList.add(evaluator);
}
}
}
Method m = FunctionRegistry.getMethodInternal(udafClass, mList, false, argClasses);
// Find the class that has this method.
// Note that Method.getDeclaringClass() may not work here because the method
// can be inherited from a base class.
int found = -1;
for (int i = 0; i < mList.size(); i++) {
if (mList.get(i) == m) {
if (found == -1) {
found = i;
} else {
throw new AmbiguousMethodException(udafClass, argClasses, mList);
}
}
}
assert (found != -1);
return cList.get(found);
}
}