MR案例之单表连接

发布 : 2016-03-20 分类 : 大数据 浏览 : 
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实例中给出child-parent（孩子——父母）表，

要求输出grandchild-grandparent（孙子——爷奶）表。

具体实现：

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在HDFS上创建目录，并上传文件数据

[root@node1 ~]# cd /opt/modules/hadoop-2.5.1/data
[root@node1 data]# vi stjoin.txt

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[root@node1 data]# hadoop fs -mkdir -p /usr/matrix/input/stjoin/
[root@node1 data]# hadoop fs -put stjoin.txt /usr/matrix/input/stjoin/

stjoinMapper.java

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package com.matrix.stjoin;

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class stjoinMapper extends Mapper<Object, Text, Text, Text> {

    /*
     *
     * map将输出分割child和parent，然后正序输出一次作为右表，
     *
     * 反序输出一次作为左表，需要注意的是在输出的value中必须
     *
     * 加上左右表的区别标识。
     *
     */
    @Override
    protected void map(Object key, Text value, Mapper<Object, Text, Text, Text>.Context context)
            throws IOException, InterruptedException {
        String childname = new String();// 孩子名称

        String parentname = new String();// 父母名称

        String relationtype = new String();// 左右表标识

// 输入的一行预处理文本

        StringTokenizer itr = new StringTokenizer(value.toString());

        String[] values = new String[2];
        System.out.println("Mapper端："+values);

        int i = 0;

        while (itr.hasMoreTokens()) {

            values[i] = itr.nextToken();

            i++;

        }

        if (values[0].compareTo("child") != 0) {

            childname = values[0];

            parentname = values[1];

// 输出左表

            relationtype = "1";

            context.write(new Text(values[1]), new Text(relationtype +

                    "+" + childname + "+" + parentname));

// 输出右表

            relationtype = "2";

            context.write(new Text(values[0]), new Text(relationtype +

                    "+" + childname + "+" + parentname));

        }
    }

}

stjoinReducer.java

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package com.matrix.stjoin;

import java.io.IOException;
import java.util.Iterator;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.Reducer.Context;

public class stjoinReducer extends Reducer<Text, Text, Text, Text> {

    public static int time = 0;

    @Override
    protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
// 输出表头

        if (0 == time) {

            context.write(new Text("grandchild"), new Text("grandparent"));

            time++;

        }

        int grandchildnum = 0;

        String[] grandchild = new String[10];

        int grandparentnum = 0;

        String[] grandparent = new String[10];

        Iterator ite = values.iterator();

        while (ite.hasNext()) {

            String record = ite.next().toString();

            int len = record.length();

            int i = 2;

            if (0 == len) {

                continue;

            }

// 取得左右表标识

            char relationtype = record.charAt(0);

// 定义孩子和父母变量

            String childname = new String();

            String parentname = new String();

// 获取value-list中value的child

            while (record.charAt(i) != '+') {

                childname += record.charAt(i);

                i++;

            }

            i = i + 1;

// 获取value-list中value的parent

            while (i < len) {

                parentname += record.charAt(i);

                i++;

            }

// 左表，取出child放入grandchildren

            if ('1' == relationtype) {

                grandchild[grandchildnum] = childname;

                grandchildnum++;

            }

// 右表，取出parent放入grandparent

            if ('2' == relationtype) {

                grandparent[grandparentnum] = parentname;

                grandparentnum++;

            }

        }

// grandchild和grandparent数组求笛卡尔儿积

        if (0 != grandchildnum && 0 != grandparentnum) {

            for (int m = 0; m < grandchildnum; m++) {

                for (int n = 0; n < grandparentnum; n++) {

// 输出结果

                    context.write(new Text(grandchild[m]), new Text(grandparent[n]));

                }

            }

        }

    }

}

stjoinTest.java

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package com.matrix.stjoin;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class stjoinTest {

    public static void main(String[] args) throws Exception {

        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://node1:8020");

        FileSystem fs = FileSystem.get(conf);

        Job job = Job.getInstance(conf);

        job.setJarByClass(stjoinTest.class);

        job.setMapperClass(stjoinMapper.class);
        job.setReducerClass(stjoinReducer.class);

// 设置Mapper输出类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(Text.class);

// 设置reducer输出类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        FileInputFormat.setInputPaths(job, "/usr/matrix/input/stjoin");

        Path outer = new Path("/usr/matrix/output/stjoin");

        if (fs.exists(outer)) {
            fs.delete(outer, true);
        }

        FileOutputFormat.setOutputPath(job, outer);

        boolean f = job.waitForCompletion(true);

        if (f) {
            System.out.println("程序执行成功！");
        }

    }
}

运行结果：

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grandchildgrandparent
TomAlice
TomJesse
JoneAlice
JoneJesse
TomBen
TomMary
JoneBen
JoneMary
PhilipAlice
PhilipJesse
MarkAlice
MarkJesse

本文作者 : Matrix
原文链接 : https://matrixsparse.github.io/2016/03/20/MR案例之单表连接/
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标签: #大数据 #MR
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