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Aggregate.TopKCombineFn (Apache Crunch 0.11.0 API)

Class Aggregate.TopKCombineFn<K,V>

  extended by org.apache.crunch.DoFn<Pair<S,Iterable<T>>,Pair<S,T>>
      extended by org.apache.crunch.CombineFn<Integer,Pair<K,V>>
          extended by org.apache.crunch.lib.Aggregate.TopKCombineFn<K,V>
All Implemented Interfaces:
Enclosing class:

public static class Aggregate.TopKCombineFn<K,V>
extends CombineFn<Integer,Pair<K,V>>

See Also:
Serialized Form

Constructor Summary
Aggregate.TopKCombineFn(int limit, boolean maximize, PType<Pair<K,V>> pairType)
Method Summary
 void initialize()
          Initialize this DoFn.
 void process(Pair<Integer,Iterable<Pair<K,V>>> input, Emitter<Pair<Integer,Pair<K,V>>> emitter)
          Processes the records from a PCollection.
Methods inherited from class org.apache.crunch.DoFn
cleanup, configure, disableDeepCopy, scaleFactor, setConfiguration, setContext
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail


public Aggregate.TopKCombineFn(int limit,
                               boolean maximize,
                               PType<Pair<K,V>> pairType)
Method Detail


public void initialize()
Description copied from class: DoFn
Initialize this DoFn. This initialization will happen before the actual DoFn.process(Object, Emitter) is triggered. Subclasses may override this method to do appropriate initialization.

Called during the setup of the job instance this DoFn is associated with.

initialize in class DoFn<Pair<Integer,Iterable<Pair<K,V>>>,Pair<Integer,Pair<K,V>>>


public void process(Pair<Integer,Iterable<Pair<K,V>>> input,
                    Emitter<Pair<Integer,Pair<K,V>>> emitter)
Description copied from class: DoFn
Processes the records from a PCollection.

Note: Crunch can reuse a single input record object whose content changes on each DoFn.process(Object, Emitter) method call. This functionality is imposed by Hadoop's Reducer implementation: The framework will reuse the key and value objects that are passed into the reduce, therefore the application should clone the objects they want to keep a copy of.

Specified by:
process in class DoFn<Pair<Integer,Iterable<Pair<K,V>>>,Pair<Integer,Pair<K,V>>>
input - The input record.
emitter - The emitter to send the output to

Copyright © 2014 The Apache Software Foundation. All Rights Reserved.