/**
* 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.util.List;
import org.apache.hadoop.hive.serde2.typeinfo.TypeInfo;
/**
* The UDF Method resolver interface. A user can plugin a resolver to their UDF
* by implementing the functions in this interface. Note that the resolver is
* stored in the UDF class as an instance variable. We did not use a static
* variable because many resolvers maintain the class of the enclosing UDF as
* state and are called from a base class e.g. UDFBaseCompare. This makes it
* very easy to write UDFs that want to do resolution similar to the comparison
* operators. Such UDFs just need to extend UDFBaseCompare and do not have to
* care about the UDFMethodResolver interface. Same is true for UDFs that want
* to do resolution similar to that done by the numeric operators. Such UDFs
* simply have to extend UDFBaseNumericOp class. For the default resolution the
* UDF implementation simply needs to extend the UDF class.
*/
public interface UDAFEvaluatorResolver {
/**
* Gets the evaluator class corresponding to the passed parameter list.
*/
Class<? extends UDAFEvaluator> getEvaluatorClass(List<TypeInfo> argClasses)
throws UDFArgumentException;
}