/**
* 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;
import java.io.IOException;
import java.util.Arrays;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.MapFile;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.SequenceFile.CompressionType;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.DefaultCodec;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.util.Progressable;
import org.apache.hadoop.util.ReflectionUtils;
/** An {@link OutputFormat} that writes {@link MapFile}s. */
public class MapFileOutputFormat extends OutputFormatBase {
public RecordWriter getRecordWriter(FileSystem ignored, JobConf job,
String name, Progressable progress)
throws IOException {
Path file = new Path(job.getOutputPath(), name);
CompressionCodec codec = null;
CompressionType compressionType = CompressionType.NONE;
if (getCompressOutput(job)) {
// find the kind of compression to do
compressionType = SequenceFileOutputFormat.getOutputCompressionType(job);
// find the right codec
Class codecClass = getOutputCompressorClass(job, DefaultCodec.class);
codec = (CompressionCodec)
ReflectionUtils.newInstance(codecClass, job);
}
// ignore the progress parameter, since MapFile is local
final MapFile.Writer out =
new MapFile.Writer(job, file.getFileSystem(job), file.toString(),
job.getOutputKeyClass(),
job.getOutputValueClass(),
compressionType, codec,
progress);
return new RecordWriter() {
public void write(WritableComparable key, Writable value)
throws IOException {
out.append(key, value);
}
public void close(Reporter reporter) throws IOException { out.close();}
};
}
/** Open the output generated by this format. */
public static MapFile.Reader[] getReaders(FileSystem ignored, Path dir,
Configuration conf)
throws IOException {
FileSystem fs = dir.getFileSystem(conf);
Path[] names = fs.listPaths(dir);
// sort names, so that hash partitioning works
Arrays.sort(names);
MapFile.Reader[] parts = new MapFile.Reader[names.length];
for (int i = 0; i < names.length; i++) {
parts[i] = new MapFile.Reader(fs, names[i].toString(), conf);
}
return parts;
}
/** Get an entry from output generated by this class. */
public static <K extends WritableComparable, V extends Writable>
Writable getEntry(MapFile.Reader[] readers,
Partitioner<K, V> partitioner,
K key,
V value) throws IOException {
int part = partitioner.getPartition(key, value, readers.length);
return readers[part].get(key, value);
}
}