org.apache.crunch.fn

Class ExtractKeyFn<K,V>

java.lang.Object

org.apache.crunch.DoFn<S,T>

org.apache.crunch.MapFn<V,Pair<K,V>>

org.apache.crunch.fn.ExtractKeyFn<K,V>

All Implemented Interfaces:

Serializable

public class ExtractKeyFn<K,V>
extends MapFn<V,Pair<K,V>>

Wrapper function for converting a key-from-value extractor MapFn<V, K> into a key-value pair extractor that is used to convert from a PCollection<V> to a PTable<K, V>.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
ExtractKeyFn(MapFn<V,K> mapFn)

Method Summary

Modifier and Type	Method and Description
void	configure(org.apache.hadoop.conf.Configuration conf) Configure this DoFn.
void	initialize() Initialize this DoFn.
Pair<K,V>	map(V input) Maps the given input into an instance of the output type.
float	scaleFactor() Returns an estimate of how applying this function to a PCollection will cause it to change in side.
void	setConfiguration(org.apache.hadoop.conf.Configuration conf) Called during the setup of an initialized PType that relies on this instance.
void	setContext(org.apache.hadoop.mapreduce.TaskInputOutputContext<?,?,?,?> context) Called during setup to pass the TaskInputOutputContext to this DoFn instance.

Methods inherited from class org.apache.crunch.MapFn

process

Methods inherited from class org.apache.crunch.DoFn

cleanup, disableDeepCopy

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ExtractKeyFn

public ExtractKeyFn(MapFn<V,K> mapFn)

Method Detail

setConfiguration

public void setConfiguration(org.apache.hadoop.conf.Configuration conf)

Description copied from class: DoFn

Called during the setup of an initialized PType that relies on this instance.

Overrides:

setConfiguration in class DoFn<V,Pair<K,V>>

Parameters:

conf - The non-null configuration for the PType being initialized

setContext

public void setContext(org.apache.hadoop.mapreduce.TaskInputOutputContext<?,?,?,?> context)

Description copied from class: DoFn

Called during setup to pass the TaskInputOutputContext to this DoFn instance. The specified TaskInputOutputContext must not be null.

Overrides:

setContext in class DoFn<V,Pair<K,V>>

configure

public void configure(org.apache.hadoop.conf.Configuration conf)

Description copied from class: DoFn

Configure this DoFn. Subclasses may override this method to modify the configuration of the Job that this DoFn instance belongs to.

Called during the job planning phase by the crunch-client.

Overrides:

configure in class DoFn<V,Pair<K,V>>

Parameters:

conf - The Configuration instance for the Job.

initialize

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.

Overrides:

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

scaleFactor

public float scaleFactor()

Description copied from class: DoFn

Returns an estimate of how applying this function to a PCollection will cause it to change in side. The optimizer uses these estimates to decide where to break up dependent MR jobs into separate Map and Reduce phases in order to minimize I/O.

Subclasses of DoFn that will substantially alter the size of the resulting PCollection should override this method.

Overrides:

scaleFactor in class MapFn<V,Pair<K,V>>

map

public Pair<K,V> map(V input)

Description copied from class: MapFn

Maps the given input into an instance of the output type.

Specified by:

map in class MapFn<V,Pair<K,V>>