org.apache.crunch.lib
Class Aggregate.TopKFn<K,V>
java.lang.Object
org.apache.crunch.DoFn<Pair<K,V>,Pair<Integer,Pair<K,V>>>
org.apache.crunch.lib.Aggregate.TopKFn<K,V>
- All Implemented Interfaces:
- Serializable
- Enclosing class:
- Aggregate
public static class Aggregate.TopKFn<K,V>
- extends DoFn<Pair<K,V>,Pair<Integer,Pair<K,V>>>
- See Also:
- Serialized Form
Aggregate.TopKFn
public Aggregate.TopKFn(int limit,
boolean ascending)
initialize
public void initialize()
- Description copied from class:
DoFn
- Called during the setup of the MapReduce job this
DoFn
is
associated with. Subclasses may override this method to do appropriate
initialization.
- Overrides:
initialize
in class DoFn<Pair<K,V>,Pair<Integer,Pair<K,V>>>
process
public void process(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<K,V>,Pair<Integer,Pair<K,V>>>
- Parameters:
input
- The input record.emitter
- The emitter to send the output to
cleanup
public void cleanup(Emitter<Pair<Integer,Pair<K,V>>> emitter)
- Description copied from class:
DoFn
- Called during the cleanup of the MapReduce job this
DoFn
is
associated with. Subclasses may override this method to do appropriate
cleanup.
- Overrides:
cleanup
in class DoFn<Pair<K,V>,Pair<Integer,Pair<K,V>>>
- Parameters:
emitter
- The emitter that was used for output
Copyright © 2012 The Apache Software Foundation. All Rights Reserved.