org.apache.tinkerpop.gremlin.process.traversal.step.map

Class GroupStep<S,K,V>

java.lang.Object

org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep<S,E>

org.apache.tinkerpop.gremlin.process.traversal.step.util.ReducingBarrierStep<S,Map<K,V>>

org.apache.tinkerpop.gremlin.process.traversal.step.map.GroupStep<S,K,V>

All Implemented Interfaces:

Serializable, AutoCloseable, Cloneable, Iterator<Traverser.Admin<Map<K,V>>>, Step<S,Map<K,V>>, Barrier<Map<K,V>>, ByModulating, Generating<Map<K,V>,Map<K,V>>, MemoryComputing<Map<K,V>>, ProfilingAware, TraversalParent

public final class GroupStep<S,K,V>
extends ReducingBarrierStep<S,Map<K,V>>
implements ByModulating, TraversalParent, ProfilingAware

Author:

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

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	GroupStep.GroupBiOperator<K,V>

Nested classes/interfaces inherited from interface org.apache.tinkerpop.gremlin.process.traversal.step.ProfilingAware

ProfilingAware.ProfiledBarrier

Field Summary

Fields inherited from class org.apache.tinkerpop.gremlin.process.traversal.step.util.ReducingBarrierStep

reducingBiOperator, seedSupplier

Fields inherited from class org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep

id, labels, nextEnd, nextStep, previousStep, starts, traversal, traverserStepIdAndLabelsSetByChild

Constructor Summary

Constructors

Constructor and Description
GroupStep(Traversal.Admin traversal)

Method Summary

Modifier and Type	Method and Description
GroupStep<S,K,V>	clone() Cloning is used to duplicate steps for the purpose of traversal optimization and OLTP replication.
static <S,E> Traversal.Admin<S,E>	convertValueTraversal(Traversal.Admin<S,E> valueTraversal)
static <S,V> Barrier	determineBarrierStep(Traversal.Admin<S,V> traversal) Determines the first (non-local) barrier step in the provided traversal.
static <K,V> Map<K,V>	doFinalReduction(Map<K,Object> map, Traversal.Admin<?,V> valueTraversal)
Map<K,V>	generateFinalResult(Map<K,V> object) Post-process the side-effect and return the post-processed side-effect.
List<Traversal.Admin<?,?>>	getLocalChildren()
Set<TraverserRequirement>	getRequirements() Provide the necessary TraverserRequirement that must be met by the traverser in order for the step to function properly.
int	hashCode()
void	modulateBy(Traversal.Admin<?,?> kvTraversal)
void	prepareForProfiling() Reset the Barrier on the step to be wrapped in a ProfiledBarrier which can properly start/stop the timer on the associated ProfileStep.
Map<K,V>	projectTraverser(Traverser.Admin<S> traverser)
void	setTraversal(Traversal.Admin<?,?> parentTraversal) Set the Traversal that this step is contained within.
String	toString()

Methods inherited from class org.apache.tinkerpop.gremlin.process.traversal.step.util.ReducingBarrierStep

addBarrier, done, getBiOperator, getMemoryComputeKey, getSeedSupplier, hasNextBarrier, nextBarrier, processAllStarts, processNextStart, reset, setReducingBiOperator, setSeedSupplier

Methods inherited from class org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep

addLabel, addStart, addStarts, equals, getId, getLabels, getNextStep, getPreviousStep, getStarts, getTraversal, hasNext, isTraverserStepIdAndLabelsSetByChild, next, prepareTraversalForNextStep, removeLabel, setId, setNextStep, setPreviousStep

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.tinkerpop.gremlin.process.traversal.step.ByModulating

modulateBy, modulateBy, modulateBy, modulateBy, modulateBy, modulateBy, modulateBy, modulateBy, modulateBy, modulateBy, modulateBy

Methods inherited from interface org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent

addGlobalChild, addLocalChild, asStep, close, getGlobalChildren, getSelfAndChildRequirements, integrateChild, removeGlobalChild, removeLocalChild

Methods inherited from interface org.apache.tinkerpop.gremlin.process.traversal.Step

equals

Methods inherited from interface java.util.Iterator

forEachRemaining, remove

Constructor Detail

GroupStep

public GroupStep(Traversal.Admin traversal)

Method Detail

determineBarrierStep

public static <S,V> Barrier determineBarrierStep(Traversal.Admin<S,V> traversal)

Determines the first (non-local) barrier step in the provided traversal. This method is used by GroupStep and GroupSideEffectStep to ultimately determine the reducing bi-operator.

Parameters:

traversal - The traversal to inspect.

Returns:

The first non-local barrier step or null if no such step was found.

prepareForProfiling

public void prepareForProfiling()

Reset the Barrier on the step to be wrapped in a ProfiledBarrier which can properly start/stop the timer on the associated ProfileStep.

Specified by:

prepareForProfiling in interface ProfilingAware

modulateBy

public void modulateBy(Traversal.Admin<?,?> kvTraversal)

Specified by:

modulateBy in interface ByModulating

projectTraverser

public Map<K,V> projectTraverser(Traverser.Admin<S> traverser)

Specified by:

projectTraverser in class ReducingBarrierStep<S,Map<K,V>>

toString

public String toString()

Overrides:

toString in class AbstractStep<S,Map<K,V>>

getLocalChildren

public List<Traversal.Admin<?,?>> getLocalChildren()

Specified by:

getLocalChildren in interface TraversalParent

getRequirements

public Set<TraverserRequirement> getRequirements()

Description copied from interface: Step

Provide the necessary TraverserRequirement that must be met by the traverser in order for the step to function properly. The provided default implements returns an empty set.

Specified by:

getRequirements in interface Step<S,Map<K,V>>

Returns:

the set of requirements

clone

public GroupStep<S,K,V> clone()

Description copied from interface: Step

Cloning is used to duplicate steps for the purpose of traversal optimization and OLTP replication. When cloning a step, it is important that the steps, the cloned step is equivalent to the state of the step when Step.reset() is called. Moreover, the previous and next steps should be set to EmptyStep.

Specified by:

clone in interface Step<S,Map<K,V>>

Overrides:

clone in class ReducingBarrierStep<S,Map<K,V>>

Returns:

The cloned step

setTraversal

public void setTraversal(Traversal.Admin<?,?> parentTraversal)

Description copied from interface: Step

Set the Traversal that this step is contained within.

Specified by:

setTraversal in interface Step<S,Map<K,V>>

Overrides:

setTraversal in class AbstractStep<S,Map<K,V>>

Parameters:

parentTraversal - the new traversal for this step

hashCode

public int hashCode()

Overrides:

hashCode in class AbstractStep<S,Map<K,V>>

generateFinalResult

public Map<K,V> generateFinalResult(Map<K,V> object)

Description copied from interface: Generating

Post-process the side-effect and return the post-processed side-effect. The default implementation is simply the identity function and returns the argument.

Specified by:

generateFinalResult in interface Generating<Map<K,V>,Map<K,V>>

Parameters:

object - the pre-processed side-effect.

Returns:

the post-processed side-effect.

convertValueTraversal

public static <S,E> Traversal.Admin<S,E> convertValueTraversal(Traversal.Admin<S,E> valueTraversal)

doFinalReduction

public static <K,V> Map<K,V> doFinalReduction(Map<K,Object> map,
                                              Traversal.Admin<?,V> valueTraversal)