com.tinkerpop.gremlin.process.computer.traversal.step.sideEffect.mapreduce

Class TraverserMapReduce

java.lang.Object

com.tinkerpop.gremlin.process.computer.util.StaticMapReduce<java.lang.Comparable,java.lang.Object,java.lang.Comparable,java.lang.Object,java.util.Iterator<java.lang.Object>>

com.tinkerpop.gremlin.process.computer.traversal.step.sideEffect.mapreduce.TraverserMapReduce

All Implemented Interfaces:

MapReduce<java.lang.Comparable,java.lang.Object,java.lang.Comparable,java.lang.Object,java.util.Iterator<java.lang.Object>>, java.lang.Cloneable

public final class TraverserMapReduce
extends StaticMapReduce<java.lang.Comparable,java.lang.Object,java.lang.Comparable,java.lang.Object,java.util.Iterator<java.lang.Object>>

Author:

Marko A. Rodriguez (http://markorodriguez.com)

Nested Class Summary

Nested classes/interfaces inherited from interface com.tinkerpop.gremlin.process.computer.MapReduce

MapReduce.MapEmitter<K,V>, MapReduce.NullObject, MapReduce.ReduceEmitter<OK,OV>, MapReduce.Stage

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	TRAVERSERS

Fields inherited from interface com.tinkerpop.gremlin.process.computer.MapReduce

MAP_REDUCE

Constructor Summary

Constructors

Constructor and Description
TraverserMapReduce(Step traversalEndStep)

Method Summary

Modifier and Type	Method and Description
boolean	doStage(MapReduce.Stage stage) A MapReduce job can be map-only, map-reduce-only, or map-combine-reduce.
boolean	equals(java.lang.Object object)
java.util.Iterator<java.lang.Object>	generateFinalResult(java.util.Iterator<KeyValue<java.lang.Comparable,java.lang.Object>> keyValues) The key/value pairs emitted by reduce() (or map() in a map-only job) can be iterated to generate a local JVM Java object.
java.util.Optional<java.util.Comparator<java.lang.Comparable>>	getMapKeySort() If a Comparator is provided, then all pairs leaving the MapReduce.MapEmitter are sorted.
java.lang.String	getMemoryKey() The results of the MapReduce job are associated with a memory-key to ultimately be stored in Memory.
int	hashCode()
void	loadState(org.apache.commons.configuration.Configuration configuration) When it is necessary to load the state of a MapReduce job, this method is called.
void	map(Vertex vertex, MapReduce.MapEmitter<java.lang.Comparable,java.lang.Object> emitter) The map() method is logically executed at all vertices in the graph in parallel.
void	reduce(java.lang.Comparable key, java.util.Iterator<java.lang.Object> values, MapReduce.ReduceEmitter<java.lang.Comparable,java.lang.Object> emitter) The reduce() method is logically on the "machine" the respective key hashes to.
java.lang.String	toString()

Methods inherited from class com.tinkerpop.gremlin.process.computer.util.StaticMapReduce

clone, storeState

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.tinkerpop.gremlin.process.computer.MapReduce

addResultToMemory, combine, createMapReduce, getReduceKeySort

Field Detail

TRAVERSERS

public static final java.lang.String TRAVERSERS

Constructor Detail

TraverserMapReduce

public TraverserMapReduce(Step traversalEndStep)

Method Detail

loadState

public void loadState(org.apache.commons.configuration.Configuration configuration)

Description copied from interface: MapReduce

When it is necessary to load the state of a MapReduce job, this method is called. This is typically required when the MapReduce job needs to be serialized to another machine. Note that what is loaded is simply the instance state, not any processed data.

It is important that the state loaded from loadState() is identical to any state created from a constructor. For those GraphComputers that do not need to use Configurations to migrate state between JVMs, the constructor will only be used.

Parameters:

configuration - the configuration to load the state of the MapReduce job from.

doStage

public boolean doStage(MapReduce.Stage stage)

Description copied from interface: MapReduce

A MapReduce job can be map-only, map-reduce-only, or map-combine-reduce. Before executing the particular stage, this method is called to determine if the respective stage is defined. This method should return true if the respective stage as a non-default method implementation.

Parameters:

stage - the stage to check for definition.

Returns:

whether that stage should be executed.

map

public void map(Vertex vertex,
                MapReduce.MapEmitter<java.lang.Comparable,java.lang.Object> emitter)

Description copied from interface: MapReduce

The map() method is logically executed at all vertices in the graph in parallel. The map() method emits key/value pairs given some analysis of the data in the vertices (and/or its incident edges).

Parameters:

vertex - the current vertex being map() processed.

emitter - the component that allows for key/value pairs to be emitted to the next stage.

reduce

public void reduce(java.lang.Comparable key,
                   java.util.Iterator<java.lang.Object> values,
                   MapReduce.ReduceEmitter<java.lang.Comparable,java.lang.Object> emitter)

Description copied from interface: MapReduce

The reduce() method is logically on the "machine" the respective key hashes to. The reduce() method combines all the values associated with the key and emits key/value pairs.

Parameters:

key - the key that has aggregated values

values - the aggregated values associated with the key

emitter - the component that allows for key/value pairs to be emitted as the final result.

getMapKeySort

public java.util.Optional<java.util.Comparator<java.lang.Comparable>> getMapKeySort()

Description copied from interface: MapReduce

If a Comparator is provided, then all pairs leaving the MapReduce.MapEmitter are sorted. The sorted results are either fed sorted to the combine/reduce-stage or as the final output. If sorting is not required, then Optional.empty() should be returned as sorting is computationally expensive. The default implementation returns Optional.empty().

Returns:

an Optional of a comparator for sorting the map output.

generateFinalResult

public java.util.Iterator<java.lang.Object> generateFinalResult(java.util.Iterator<KeyValue<java.lang.Comparable,java.lang.Object>> keyValues)

Description copied from interface: MapReduce

The key/value pairs emitted by reduce() (or map() in a map-only job) can be iterated to generate a local JVM Java object.

Parameters:

keyValues - the key/value pairs that were emitted from reduce() (or map() in a map-only job)

Returns:

the resultant object formed from the emitted key/values.

getMemoryKey

public java.lang.String getMemoryKey()

Description copied from interface: MapReduce

The results of the MapReduce job are associated with a memory-key to ultimately be stored in Memory.

Returns:

the memory key of the generated result object.

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

equals

public boolean equals(java.lang.Object object)

Overrides:

equals in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class StaticMapReduce<java.lang.Comparable,java.lang.Object,java.lang.Comparable,java.lang.Object,java.util.Iterator<java.lang.Object>>