Hadoop和HBase的新功能。讓我用一個例子來解釋我的問題。爲簡潔起見,數據變得很小。從Reducer中的HBase中讀取數據
假設我們有一個名爲item.log的文件,它包含以下信息。
ITEM-1,PRODUCT-1 ITEM-2,PRODUCT-1 ITEM-3,PRODUCT-2 ITEM-4,PRODUCT-2 ITEM-5,PRODUCT-3 ITEM-6,PRODUCT-1 ITEM-7,PRODUCT-1 ITEM-8,PRODUCT-2 ITEM-9,PRODUCT-1
我有如下的地圖減少代碼,
package org.sanjus.hadoop;
import java.io.IOException;
import java.util.Iterator;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;
public class ProductMapReduce {
public static class Map extends MapReduceBase implements Mapper<LongWritable, Text, Text, LongWritable> {
public void map(LongWritable key, Text value, OutputCollector<Text, LongWritable> output, Reporter reporter) throws IOException {
String[] columns = value.toString().split(",");
if (columns.length != 2) {
System.out.println("Bad line/value " + value);
return;
}
Text word = new Text(columns[1]);
LongWritable counter = new LongWritable(1L);
output.collect(word, counter);
}
}
public static class Reduce extends MapReduceBase implements Reducer<Text, LongWritable, Text, LongWritable> {
public void reduce(Text key, Iterator<LongWritable> iterator, OutputCollector<Text, LongWritable> output, Reporter reporter) throws IOException {
long sum = 0L;
while (iterator.hasNext()) {
sum += iterator.next().get();
}
output.collect(key, new LongWritable(sum));
}
}
public static void main(String[] args) throws IOException {
JobConf conf = new JobConf(ProductMapReduce.class);
conf.setJobName("Product Analyzer");
conf.setOutputKeyClass(Text.class);
conf.setOutputValueClass(LongWritable.class);
conf.setMapperClass(Map.class);
conf.setCombinerClass(Reduce.class);
conf.setReducerClass(Reduce.class);
conf.setInputFormat(TextInputFormat.class);
conf.setOutputFormat(TextOutputFormat.class);
FileInputFormat.setInputPaths(conf, new Path(args[0]));
FileOutputFormat.setOutputPath(conf, new Path(args[1]));
JobClient.runJob(conf);
}
}
LABEL 1:地圖後輸出減少低於:
PRODUCT-1 5 PRODUCT-2 3 PRODUCT-3 1
這裏是一個問題:
我在HBase中有一個表,它具有以下信息如下。
PRODUCT-1 10$ PRODUCT-2 20$ PRODUCT-3 30$
問題/需求:我想要的降低相的輸出作爲減少輸出的合併在「LABEL 1:」及以上
HBase的表中規定PRODUCT-1 10$ * 5 = 50$ PRODUCT-2 20$ * 3 = 60$ PRODUCT-3 30$ * 1 = 30$
基本上,密鑰是PRODUCT-1,該密鑰的值爲10 $,同一密鑰的值爲5,兩個值相乘。 ($符號是爲了解)
注:我發現的例子是基於輸入或輸出到HBase。我的情況是,輸入和輸出將是HDFS中的文件,而我需要使用HBase表中的信息處理reducer輸出。
在你的reducer中,你擴展了TableReducer類嗎? – Shash
@shash,我在我的reduce實現中擴展了'org.apache.hadoop.mapreduce.Reducer'類。 –