org.apache.crunch.lib.join

Class LeftOuterJoinFn<K,U,V>

java.lang.Object

org.apache.crunch.DoFn<Pair<Pair<K,Integer>,Iterable<Pair<U,V>>>,Pair<K,Pair<U,V>>>

org.apache.crunch.lib.join.JoinFn<K,U,V>

org.apache.crunch.lib.join.LeftOuterJoinFn<K,U,V>

Type Parameters:

K - Type of the keys.

U - Type of the first PTable's values

V - Type of the second PTable's values

All Implemented Interfaces:

Serializable

public class LeftOuterJoinFn<K,U,V>
extends JoinFn<K,U,V>

Used to perform the last step of an left outer join.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
LeftOuterJoinFn(PType<K> keyType, PType<U> leftValueType)

Method Summary

Modifier and Type	Method and Description
void	cleanup(Emitter<Pair<K,Pair<U,V>>> emitter) Called during the cleanup of the MapReduce job this DoFn is associated with.
String	getJoinType()
void	initialize() Initialize this DoFn.
void	join(K key, int id, Iterable<Pair<U,V>> pairs, Emitter<Pair<K,Pair<U,V>>> emitter) Performs the actual joining.

Methods inherited from class org.apache.crunch.lib.join.JoinFn

process

Methods inherited from class org.apache.crunch.DoFn

configure, disableDeepCopy, scaleFactor, setConfiguration, setContext

Methods inherited from class java.lang.Object

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

Constructor Detail

LeftOuterJoinFn

public LeftOuterJoinFn(PType<K> keyType,
                       PType<U> leftValueType)

Method Detail

initialize

public void initialize()

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 JoinFn<K,U,V>

join

public void join(K key,
                 int id,
                 Iterable<Pair<U,V>> pairs,
                 Emitter<Pair<K,Pair<U,V>>> emitter)

Performs the actual joining.

Specified by:

join in class JoinFn<K,U,V>

Parameters:

key - The key for this grouping of values.

id - The side that this group of values is from (0 -> left, 1 -> right).

pairs - The group of values associated with this key and id pair.

emitter - The emitter to send the output to.

cleanup

public void cleanup(Emitter<Pair<K,Pair<U,V>>> emitter)

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<Pair<K,Integer>,Iterable<Pair<U,V>>>,Pair<K,Pair<U,V>>>

Parameters:

emitter - The emitter that was used for output

getJoinType

public String getJoinType()

Specified by:

getJoinType in class JoinFn<K,U,V>

Returns:

The name of this join type (e.g. innerJoin, leftOuterJoin).