/*
 * 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.hbase.mapreduce;

import org.apache.hadoop.hbase.client.Mutation;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * Extends the basic <code>Reducer</code> class to add the required key and value input/output
 * classes. While the input key and value as well as the output key can be anything handed in from
 * the previous map phase the output value <u>must</u> be either a
 * {@link org.apache.hadoop.hbase.client.Put Put} or a {@link org.apache.hadoop.hbase.client.Delete
 * Delete} instance when using the {@link TableOutputFormat} class.
 * <p>
 * This class is extended by {@link IdentityTableReducer} but can also be subclassed to implement
 * similar features or any custom code needed. It has the advantage to enforce the output value to a
 * specific basic type.
 * @param <KEYIN>   The type of the input key.
 * @param <VALUEIN> The type of the input value.
 * @param <KEYOUT>  The type of the output key.
 * @see org.apache.hadoop.mapreduce.Reducer
 */
@InterfaceAudience.Public
public abstract class TableReducer<KEYIN, VALUEIN, KEYOUT>
  extends Reducer<KEYIN, VALUEIN, KEYOUT, Mutation> {
}
