Home | About | Sematext search-lucene.com search-hadoop.com
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB
 Search Hadoop and all its subprojects:

Switch to Threaded View
HDFS >> mail # user >> RE: objects as key/values


Copy link to this message
-
RE: objects as key/values
You can write custom key/value classes by implementing org.apache.hadoop.io.Writable interface for your Job.

http://hadoop.apache.org/docs/current/api/org/apache/hadoop/io/Writable.html

Thanks
Devaraj k

From: jamal sasha [mailto:[EMAIL PROTECTED]]
Sent: 30 July 2013 10:27
To: [EMAIL PROTECTED]
Subject: objects as key/values

Ok.
  A very basic (stupid) question.
I am trying to compute mean using hadoop.

So my implementation is like this:

public class Mean
 public static class Pair{
  //simple class to create object
}
 public class MeanMapper<LongWritable, Text,Text, Pair>
   emit(text,pair) //where pair is (local sum, count)

 public class MeanReducer<Text, Pair, Text DoubleWritable>
    emit (text, mean)

Unfortunately such approach of creating custom class types are not working
since in job I have to set the output type for mapper/reducer...
How are custom key values pair implemented in hadoop?
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB