Package 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>>, Grouping<S,K,V>, MemoryComputing<Map<K,V>>, PopContaining, TraversalParent

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

Author:

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

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

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

Nested classes/interfaces inherited from class org.apache.tinkerpop.gremlin.process.traversal.step.util.ReducingBarrierStep

ReducingBarrierStep.NonEmittingSeed

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

PopContaining.PopInstruction

Field Summary

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

hasProcessedOnce, NON_EMITTING_SEED, 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	Description
GroupStep(Traversal.Admin traversal)

Method Summary

Modifier and Type	Method	Description
GroupStep<S,K,V>	clone()	Cloning is used to duplicate steps for the purpose of traversal optimization and OLTP replication.
Map<K,V>	generateFinalResult(Map<K,V> object)	Post-process the side-effect and return the post-processed side-effect.
Traversal.Admin<S,K>	getKeyTraversal()	Determines if the provided traversal is equal to the key traversal that the Grouping has.
List<Traversal.Admin<?,?>>	getLocalChildren()	Gets a list of all "local" child traversals for this step.
Set<TraverserRequirement>	getRequirements()	Provide the necessary TraverserRequirement that must be met by the traverser in order for the step to function properly.
Traversal.Admin<S,V>	getValueTraversal()	Determines if the provided traversal is equal to the value traversal that the Grouping has.
int	hashCode()
void	modulateBy(Traversal.Admin<?,?> kvTraversal)
Map<K,V>	projectTraverser(Traverser.Admin<S> traverser)
void	replaceLocalChild(Traversal.Admin<?,?> oldTraversal, Traversal.Admin<?,?> newTraversal)
void	resetBarrierFromValueTraversal()	The first non-local Barrier step ascertained by calls to Grouping.determineBarrierStep(Traversal.Admin) is cached for a Grouping.
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, generateSeedFromStarts, getBiOperator, getEmptyBarrier, 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, clearLabels, equals, getId, getLabels, getNextStep, getPreviousStep, getStarts, getTraversal, hasNext, hasStarts, 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.Grouping

convertValueTraversal, determineBarrierStep, doFinalReduction, hasBarrierInValueTraversal

Methods inherited from interface java.util.Iterator

forEachRemaining, remove

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

equals

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

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

Constructor Details

GroupStep

public GroupStep(Traversal.Admin traversal)

Method Details

getKeyTraversal

public Traversal.Admin<S,K> getKeyTraversal()

Description copied from interface: Grouping

Determines if the provided traversal is equal to the key traversal that the Grouping has.

Specified by:

getKeyTraversal in interface Grouping<S,K,V>

getValueTraversal

public Traversal.Admin<S,V> getValueTraversal()

Description copied from interface: Grouping

Determines if the provided traversal is equal to the value traversal that the Grouping has.

Specified by:

getValueTraversal in interface Grouping<S,K,V>

resetBarrierFromValueTraversal

public void resetBarrierFromValueTraversal()

Description copied from interface: Grouping

The first non-local Barrier step ascertained by calls to Grouping.determineBarrierStep(Traversal.Admin) is cached for a Grouping. After strategy application it is important that the cache be reset to ensure that any modifications to the child traversal are accounted for.

Specified by:

resetBarrierFromValueTraversal in interface Grouping<S,K,V>

modulateBy

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

Specified by:

modulateBy in interface ByModulating

replaceLocalChild

public void replaceLocalChild(Traversal.Admin<?,?> oldTraversal,
 Traversal.Admin<?,?> newTraversal)

Specified by:

replaceLocalChild in interface TraversalParent

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()

Description copied from interface: TraversalParent

Gets a list of all "local" child traversals for this step. A "local" traversal is one which is evaluated independently for each incoming traverser to the parent step. This is typically used in cases where the child is used to process or augment each traverser individually. See LocalStep or ByModulating as examples.

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,K>

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,K>

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,K>

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<S,K>

Parameters:

object - the pre-processed side-effect.

Returns:

the post-processed side-effect.