001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.mapred.lib;
020
021import org.apache.hadoop.classification.InterfaceAudience;
022import org.apache.hadoop.classification.InterfaceStability;
023import org.apache.hadoop.mapred.JobConf;
024import org.apache.hadoop.mapred.JobConfigurable;
025import org.apache.hadoop.mapreduce.JobContext;
026
027/**
028 * This comparator implementation provides a subset of the features provided
029 * by the Unix/GNU Sort. In particular, the supported features are:
030 * -n, (Sort numerically)
031 * -r, (Reverse the result of comparison)
032 * -k pos1[,pos2], where pos is of the form f[.c][opts], where f is the number
033 *  of the field to use, and c is the number of the first character from the
034 *  beginning of the field. Fields and character posns are numbered starting
035 *  with 1; a character position of zero in pos2 indicates the field's last
036 *  character. If '.c' is omitted from pos1, it defaults to 1 (the beginning
037 *  of the field); if omitted from pos2, it defaults to 0 (the end of the
038 *  field). opts are ordering options (any of 'nr' as described above). 
039 * We assume that the fields in the key are separated by
040 * {@link JobContext#MAP_OUTPUT_KEY_FIELD_SEPERATOR} 
041 */
042@InterfaceAudience.Public
043@InterfaceStability.Stable
044public class KeyFieldBasedComparator<K, V> extends 
045    org.apache.hadoop.mapreduce.lib.partition.KeyFieldBasedComparator<K, V>
046    implements JobConfigurable {
047
048  public void configure(JobConf job) {
049    super.setConf(job);
050  }
051}