Home > Software > BIGDATA > HADOOP
Interview Questions   Tutorials   Discussions   Programs   Videos   Discussion   

HADOOP - Explain the Reducer?s reduce phase?




547
views
asked SRVMTrainings November 11, 2012 02:25 AM  

Explain the Reducer?s reduce phase?


           

1 Answers



 
answered By   0  
Reducer has 3 primary phases: shuffle, sort and reduce.

Reduce

In this phase the 
reduce(MapOutKeyType, Iterable<MapOutValType>, Context) method is called for each <key, (list of values)> pair in the grouped inputs.

The output of the reduce task is typically written to the FileSystem via Context.write(ReduceOutKeyType, ReduceOutValType).

Applications can use the Context to report progress, set application-level status messages and update Counters, or just indicate that they are alive.

The output of the Reducer is not sorted.

flag   
   add comment

Your answer

Join with account you already have

FF

Preview


Ready to start your tutorial with us? That's great! Send us an email and we will get back to you as soon as possible!

Alert