MapFileOutputFormat.java
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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.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.fs.FileUtil;
- 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 FileOutputFormat<WritableComparable, Writable> {
- public RecordWriter<WritableComparable, Writable> getRecordWriter(FileSystem ignored, JobConf job,
- String name, Progressable progress)
- throws IOException {
- // get the path of the temporary output file
- Path file = FileOutputFormat.getTaskOutputPath(job, name);
-
- FileSystem fs = file.getFileSystem(job);
- 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<? extends CompressionCodec> codecClass = getOutputCompressorClass(job,
- DefaultCodec.class);
- codec = ReflectionUtils.newInstance(codecClass, job);
- }
-
- // ignore the progress parameter, since MapFile is local
- final MapFile.Writer out =
- new MapFile.Writer(job, fs, file.toString(),
- job.getOutputKeyClass().asSubclass(WritableComparable.class),
- job.getOutputValueClass().asSubclass(Writable.class),
- compressionType, codec,
- progress);
- return new RecordWriter<WritableComparable, Writable>() {
- 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 = FileUtil.stat2Paths(fs.listStatus(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);
- }
- }