MR Lab3

grouping By Multiple columns.

ex:

 select dno, sex, sum(sal) from emp
   group by dno, sex;


DnoSexSalMap.java
--------------------
package mr.analytics;

import java.io.IOException;

import
org.apache.hadoop.io.IntWritable;
import
org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import
org.apache.hadoop.mapreduce.Mapper;
public class DnoSexSalMap extends

Mapper
 <LongWritable,Text,Text,IntWritable>
{
     //  file : emp
     // schema : id,name,sal,sex,dno
    //  delimiter : "," (comma)
 //  sample row : 101,amar,20000,m,11
 //   sex as key, sal as value.
    public void map(LongWritable 
k,Text v,
            Context  con)
     throws IOException,
InterruptedException
     {
        String line =
v.toString();
      String[] w = line.split(",");   
      String sex = w[3];
      String dno = w[4];
      String myKey = dno+"\t"+sex;
     int sal =Integer.parseInt(w[2]);
    con.write(new Text(myKey),new
IntWritable(sal));
     }
  }

----------------
Driver8.java
----------------

package mr.analytics;

import

org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import

org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import

org.apache.hadoop.mapreduce.lib.input.F

ileInputFormat;
import

org.apache.hadoop.mapreduce.lib.output.

FileOutputFormat;

public class Driver8
{
    public static void main(String

[] args)
     throws Exception
     {
        Configuration c = new

Configuration();
        Job j = new Job

(c,"d8");
        j.setJarByClass

(Driver8.class);
        j.setMapperClass

(DnoSexSalMap.class);
        j.setReducerClass

(RedForSum.class);
        j.setOutputKeyClass

(Text.class);
        j.setOutputValueClass

(IntWritable.class);
         Path p1 = new Path

(args[0]); //input
         Path p2 = new Path

(args[1]); //output
       
FileInputFormat.addInputPath(j,p1);
FileOutputFormat.setOutputPath(j, p2);

System.exit(j.waitForCompletion(true) ?

0:1);
  }
}

--------------------------

submit:

[training@localhost ~]$ hadoop fs -cat

mrlab/r8/part-r-00000
11      f       25000
11      m       26000
12      f       18000
13      m       19000

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