[SequenceFile_3] MapFile

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0. 说明

　　MapFile 介绍 && 测试

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1. 介绍

　　对 MapFile 的介绍如下：

1. MapFile 是带有索引的 SequenceFile
2. MapFile 是排序的 SequenceFile

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2. 测试

package hadoop.sequencefile;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.FileSystem;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.MapFile;

import org.apache.hadoop.io.Text;

import org.junit.Test;

/**

 * 测试 MapFile 操作

 * Windows 下查看压缩后的 MapFile :

 * hdfs dfs -text file:///E:/test/mapfile/index

 * hdfs dfs -text file:///E:/test/mapfile/data

 */

public class TestMapFile {

    /**

     * 测试序列文件写操作

     */

    @Test

    public void testWriteSeq() throws Exception {

        Configuration conf = new Configuration();

        // 设置文件系统为本地模式

        conf.set("fs.defaultFS", "file:///");

        FileSystem fs = FileSystem.get(conf);

        // 数据存放的文件夹路径

        String path = "E:/test/mapfile";

        MapFile.Writer writer = new MapFile.Writer(conf, fs, path, IntWritable.class, Text.class);

        for (int i = 1; i <= 100; i++) {

            IntWritable key = new IntWritable(i);

            Text value = new Text("helloworld" + i);

            writer.append(key, value);

        }

        writer.close();

    }

    /**

     * SequenceFile 转换为 MapFile

     * 新建文件夹 E:/test/mapfile2

     * 将 SequenceFile 放入其中并重命名为 data

     */

    @Test

    public void SeqConvert() throws Exception {

        System.setProperty("HADOOP_USER_NAME", "centos");

        Configuration conf = new Configuration();

        conf.set("fs.defaultFS", "file:///");

        FileSystem fs = FileSystem.get(conf);

        Path p = new Path("file:///E:/test/mapfile2");

        long cnt = MapFile.fix(fs, p, IntWritable.class, Text.class, false, conf);

        System.out.println(cnt);

    }

}

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