org.apache.hadoop.mapred.MapFileOutputFormat.java Source code

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Here is the source code for org.apache.hadoop.mapred.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 org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

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.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
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.
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
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 {
        return org.apache.hadoop.mapreduce.lib.output.MapFileOutputFormat.getReaders(dir, conf);
    }

    /** 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 readerLength = readers.length;
        int part;
        if (readerLength <= 1) {
            part = 0;
        } else {
            part = partitioner.getPartition(key, value, readers.length);
        }
        return readers[part].get(key, value);
    }

}