udf/src/java/org/apache/hadoop/hive/ql/exec/UDAFEvaluator.java

/*
 * 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;

/**
 * Interface that encapsulates the evaluation logic of a UDAF. One evaluator is
 * needed for every overloaded form of a UDAF .e.g max and min UDAFs would have
 * evaluators for integer, string and other types. On the other hand avg would
 * have an evaluator only for the double type.
 */
public interface UDAFEvaluator {

  /**
   * Initializer. Initializes the state for the evaluator.
   */
  void init();
}