hadoop KeyFieldBasedComparator 源码
haddop KeyFieldBasedComparator 代码
文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/lib/KeyFieldBasedComparator.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.mapred.lib;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.JobConfigurable;
import org.apache.hadoop.mapreduce.JobContext;
/**
* This comparator implementation provides a subset of the features provided
* by the Unix/GNU Sort. In particular, the supported features are:
* -n, (Sort numerically)
* -r, (Reverse the result of comparison)
* -k pos1[,pos2], where pos is of the form f[.c][opts], where f is the number
* of the field to use, and c is the number of the first character from the
* beginning of the field. Fields and character posns are numbered starting
* with 1; a character position of zero in pos2 indicates the field's last
* character. If '.c' is omitted from pos1, it defaults to 1 (the beginning
* of the field); if omitted from pos2, it defaults to 0 (the end of the
* field). opts are ordering options (any of 'nr' as described above).
* We assume that the fields in the key are separated by
* {@link JobContext#MAP_OUTPUT_KEY_FIELD_SEPARATOR}
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class KeyFieldBasedComparator<K, V> extends
org.apache.hadoop.mapreduce.lib.partition.KeyFieldBasedComparator<K, V>
implements JobConfigurable {
public void configure(JobConf job) {
super.setConf(job);
}
}
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