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This module contains implementations of InputFormat, OutputFormat, Mapper, Reducer, etc which are needed for running MR jobs on tables, WALs, HFiles and other HBase specific constructs. It also contains a bunch of tools: RowCounter, ImportTsv, Import, Export, CompactionTool, ExportSnapshot, WALPlayer, etc

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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.hbase.mapreduce;

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

/**
 * Extends the basic Reducer 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 must 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.
 * 
 * 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    The type of the input key.
 * @param  The type of the input value.
 * @param   The type of the output key.
 * @see org.apache.hadoop.mapreduce.Reducer
 */
@InterfaceAudience.Public
public abstract class TableReducer
  extends Reducer {
}