Haoop selfjoin 左表 右表 自连接
Haoop selfjoin 左表 右表 自连接
map
context.write写2次，作为左表、右表
左表：
context.write(new Text(array[1].trim()), new Text("1_"+array[0].trim()));
左表第一列是父亲，第二列是孩子；
右表：
context.write(new Text(array[0].trim()), new Text("0_"+array[1].trim()));
右表第一列是孩子，第二列是父亲；
reduce：
判断孩子还是父亲，生成grandChildList和grandParentList，做笛卡尔积
1、数据文件
1列是孩子 2列是父亲，找祖父亲
[root@master IMFdatatest]#hadoop dfs -cat /library/selfjoin/selfjoin.txt
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.
16/02/20 17:22:07 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Tom Lucy
Tom Jack
Jone Lucy
Jone Jack
Lucy Mary
Lucy Ben
Jack Alice
Jack Jesse
Terry Alice
Terry Jesse
Philip Terry
Philip Alma
Mark Terry
Mark Alma
2、上传hdfs
3、结果
[root@master IMFdatatest]#hadoop dfs -cat /library/outputselfjoin3/part-r-00000
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.
16/02/20 18:33:40 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Tom Alice
Tom Jesse
Jone Alice
Jone Jesse
Tom Ben
Tom Mary
Jone Ben
Jone Mary
Philip Alice
Philip Jesse
Mark Alice
Mark Jesse
打的日志
map key array[1]: Lucy value array[0]: 1_Tom
map key array[0]: Tom value array[1]: 0_Lucy
map key array[1]: Jack value array[0]: 1_Tom
map key array[0]: Tom value array[1]: 0_Jack
map key array[1]: Lucy value array[0]: 1_Jone
map key array[0]: Jone value array[1]: 0_Lucy
map key array[1]: Jack value array[0]: 1_Jone
map key array[0]: Jone value array[1]: 0_Jack
map key array[1]: Mary value array[0]: 1_Lucy
map key array[0]: Lucy value array[1]: 0_Mary
map key array[1]: Ben value array[0]: 1_Lucy
map key array[0]: Lucy value array[1]: 0_Ben
map key array[1]: Alice value array[0]: 1_Jack
map key array[0]: Jack value array[1]: 0_Alice
map key array[1]: Jesse value array[0]: 1_Jack
map key array[0]: Jack value array[1]: 0_Jesse
map key array[1]: Alice value array[0]: 1_Terry
map key array[0]: Terry value array[1]: 0_Alice
map key array[1]: Jesse value array[0]: 1_Terry
map key array[0]: Terry value array[1]: 0_Jesse
map key array[1]: Terry value array[0]: 1_Philip
map key array[0]: Philip value array[1]: 0_Terry
map key array[1]: Alma value array[0]: 1_Philip
map key array[0]: Philip value array[1]: 0_Alma
map key array[1]: Terry value array[0]: 1_Mark
map key array[0]: Mark value array[1]: 0_Terry
map key array[1]: Alma value array[0]: 1_Mark
map key array[0]: Mark value array[1]: 0_Alma
4 代码
package com.dtspark.hadoop.hellomapreduce;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
public class SelfJoin {
public static class DataMapper
extends Mapper
public void map(LongWritable key, Text value, Context context
) throws IOException, InterruptedException {
System.out.println("Map Methond Invoked!!!");
// String[] array =new String[2];
// int i=0;
String[] array;
array = value.toString().split("\t");
StringTokenizer stringTokenizer=new StringTokenizer(value.toString());
/* while(stringTokenizer.hasMoreElements()){
array[i] =stringTokenizer.nextToken().trim();
i++;
}*/
// System.out.println("key "+array[1] + "value: "+"1_"+array[0]+"_"+array[1]);
// System.out.println("key "+array[0] + "value: "+"0_"+array[0]+"_"+array[1]);
// context.write(new Text(array[1]), new Text("1_"+array[0]+"_"+array[1]));
// context.write(new Text(array[0]), new Text("0_"+array[0]+"_"+array[1]));
System.out.println("map key array[1]: " +array[1].trim() +" value array[0]: " + "1_"+array[0].trim());
System.out.println("map key array[0]: " +array[0].trim() +" value array[1]: " + "0_"+array[1].trim());
context.write(new Text(array[1].trim()), new Text("1_"+array[0].trim())); //left
context.write(new Text(array[0].trim()), new Text("0_"+array[1].trim())); //right
}
}
public static class DataReducer
extends Reducer
public void reduce(Text key, Iterable
Context context
) throws IOException, InterruptedException {
System.out.println("Reduce Methond Invoked!!!" );
Iterator
List
List
while(iterator.hasNext()){
String item = iterator.next().toString();
String[] splited = item.split("_");
if (splited[0].equals("1")){
grandChildList.add(splited[1]);
} else {
grandParentList.add(splited[1]);
}
}
if (grandChildList.size() > 0 && grandParentList.size() > 0){
for (String grandChild:grandChildList ) {
for (String grandParent: grandParentList) {
// context.write(new Text(grandChild),new Text(grandParent));
context.write(new Text(grandChild), new Text (grandParent));
}
}
}
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length < 2) {
System.err.println("Usage: JoinImproved
System.exit(2);
}
Job job = Job.getInstance(conf, "JoinImproved");
job.setJarByClass(SelfJoin.class);
job.setMapperClass(DataMapper.class);
job.setReducerClass(DataReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(Text.class);
for (int i = 0; i < otherArgs.length - 1; ++i) {
FileInputFormat.addInputPath(job, new Path(otherArgs[i]));
}
FileOutputFormat.setOutputPath(job,
new Path(otherArgs[otherArgs.length - 1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}