Package org.apache.tinkerpop.gremlin.process.traversal.traverser.util

Class EmptyTraverser<T>

java.lang.Object

org.apache.tinkerpop.gremlin.process.traversal.traverser.util.EmptyTraverser<T>

All Implemented Interfaces:

Serializable, Cloneable, Comparable<Traverser<T>>, Traverser<T>, Traverser.Admin<T>, Attachable<T>

Direct Known Subclasses:

DummyTraverser

public class EmptyTraverser<T>
extends Object
implements Traverser<T>, Traverser.Admin<T>

A Traverser with no bulk which effectively means that it will no longer be propagated through a Traversal.

Author:

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

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.tinkerpop.gremlin.structure.util.Attachable

Attachable.Exceptions, Attachable.Method

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

Traverser.Admin<T>

Field Summary

Fields inherited from interface org.apache.tinkerpop.gremlin.structure.util.Attachable

logger

Fields inherited from interface org.apache.tinkerpop.gremlin.process.traversal.Traverser.Admin

HALT

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	EmptyTraverser()

Method Summary

Modifier and Type	Method	Description
void	addLabels(Set<String> labels)
T	attach(Function<Attachable<T>,T> method)	Regenerate the detached traverser given its location at a particular vertex.
long	bulk()	A traverser may represent a grouping of traversers to allow for more efficient data propagation.
EmptyTraverser<T>	clone()	Traverser cloning is important when splitting a traverser at a bifurcation point in a traversal.
Traverser.Admin<T>	detach()	Prepare the traverser for migration across a JVM boundary.
void	dropLabels(Set<String> labels)	Drop all path information associated with specified labels.
void	dropPath()	Drop the path of the traverser.
boolean	equals(Object object)
T	get()	Get the object that the traverser is current at.
TraversalSideEffects	getSideEffects()	Get the sideEffects associated with the traversal of the traverser.
String	getStepId()	Get the step id of where the traverser is located.
Set<String>	getTags()	Get the tags associated with the traverser.
int	hashCode()
void	incrLoops()	Increment the number of times the traverser has gone through a looping section of traversal.
void	initialiseLoops(String stepLabel, String loopNam)	Initialise a loop by setting up the looping construct.
static <R> EmptyTraverser<R>	instance()	The empty Traverser instance.
void	keepLabels(Set<String> labels)	Drop all path information not associated with specified labels.
int	loops()	Return the number of times the traverser has gone through a looping section of a traversal.
int	loops(String loopName)	Return the number of times the traverser has gone through the named looping section of a traversal.
void	merge(Traverser.Admin<?> other)	When two traversers are have equality with each other, then they can be merged.
Path	path()	Get the current path of the traverser.
void	resetLoops()	Set the number of times the traverser has gone through a loop back to 0.
<S> S	sack()	Get the sack local sack object of this traverser.
<S> void	sack(S object)	Set the traversers sack object to the provided value ("sack the value").
void	set(T t)	Set the current object location of the traverser.
void	setBulk(long count)	Set the number of traversers represented by this traverser.
void	setSideEffects(TraversalSideEffects sideEffects)	Set the sideEffects of the Traversal.
void	setStepId(String stepId)	Set the step id of where the traverser is located.
Traverser.Admin<T>	split()	Generate a sibling traverser of the current traverser with a full copy of all state within the sibling.
<R> Traverser.Admin<R>	split(R r, Step<T,R> step)	Generate a child traverser of the current traverser for current as step and new object location.

Methods inherited from class java.lang.Object

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

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

asAdmin, compareTo, path, path, sideEffects, sideEffects

Methods inherited from interface org.apache.tinkerpop.gremlin.process.traversal.Traverser.Admin

getLoopNames, isHalted

Constructor Detail

EmptyTraverser

protected EmptyTraverser()

Method Detail

instance

public static <R> EmptyTraverser<R> instance()

The empty Traverser instance.

addLabels

public void addLabels(Set<String> labels)

Specified by:

addLabels in interface Traverser.Admin<T>

keepLabels

public void keepLabels(Set<String> labels)

Description copied from interface: Traverser.Admin

Drop all path information not associated with specified labels. This is an optimization method that allows a traverser to save memory and increase the likelihood of bulking.

Specified by:

keepLabels in interface Traverser.Admin<T>

Parameters:

labels - the labels to keep path information for.

dropLabels

public void dropLabels(Set<String> labels)

Description copied from interface: Traverser.Admin

Drop all path information associated with specified labels. This is an optimization method that allows a traverser to save memory and increase the likelihood of bulking.

Specified by:

dropLabels in interface Traverser.Admin<T>

Parameters:

labels - the labels to drop path information for.

dropPath

public void dropPath()

Description copied from interface: Traverser.Admin

Drop the path of the traverser. This is an optimization method that allows a traverser to save memory and increase the likelihood of bulking.

Specified by:

dropPath in interface Traverser.Admin<T>

set

public void set(T t)

Description copied from interface: Traverser.Admin

Set the current object location of the traverser.

Specified by:

set in interface Traverser.Admin<T>

Parameters:

t - The current object of the traverser

initialiseLoops

public void initialiseLoops(String stepLabel,
                            String loopNam)

Description copied from interface: Traverser.Admin

Initialise a loop by setting up the looping construct. The step label is important to create a stack of loop counters when within a nested context. If the provided label is not the same as the current label on the stack, add a new loop counter. The loopName can be used to refer to the loops counter via the LoopsStep

Specified by:

initialiseLoops in interface Traverser.Admin<T>

Parameters:

stepLabel - the label of the step that is being set-up.

loopNam - the user defined name for referencing the loop counter or null if not set

incrLoops

public void incrLoops()

Description copied from interface: Traverser.Admin

Increment the number of times the traverser has gone through a looping section of traversal.

Specified by:

incrLoops in interface Traverser.Admin<T>

resetLoops

public void resetLoops()

Description copied from interface: Traverser.Admin

Set the number of times the traverser has gone through a loop back to 0. When a traverser exits a looping construct, this method should be called. In a nested loop context, the highest stack loop counter should be removed.

Specified by:

resetLoops in interface Traverser.Admin<T>

getStepId

public String getStepId()

Description copied from interface: Traverser.Admin

Get the step id of where the traverser is located. This is typically used in multi-machine systems that require the movement of traversers between different traversal instances.

Specified by:

getStepId in interface Traverser.Admin<T>

Returns:

The future step for the traverser

setStepId

public void setStepId(String stepId)

Description copied from interface: Traverser.Admin

Set the step id of where the traverser is located. If the future is Traverser.Admin.HALT, then Traverser.Admin.isHalted() is true.

Specified by:

setStepId in interface Traverser.Admin<T>

Parameters:

stepId - The future step of the traverser

setBulk

public void setBulk(long count)

Description copied from interface: Traverser.Admin

Set the number of traversers represented by this traverser.

Specified by:

setBulk in interface Traverser.Admin<T>

Parameters:

count - the number of traversers

split

public <R> Traverser.Admin<R> split(R r,
                                    Step<T,R> step)

Description copied from interface: Traverser.Admin

Generate a child traverser of the current traverser for current as step and new object location. The child has the path history, future, and loop information of the parent. The child extends that path history with the current as and provided R-object.

Specified by:

split in interface Traverser.Admin<T>

Type Parameters:

R - The current object type of the child

Parameters:

r - The current object of the child

step - The step yielding the split

Returns:

The split traverser

split

public Traverser.Admin<T> split()

Description copied from interface: Traverser.Admin

Generate a sibling traverser of the current traverser with a full copy of all state within the sibling.

Specified by:

split in interface Traverser.Admin<T>

Returns:

The split traverser

detach

public Traverser.Admin<T> detach()

Description copied from interface: Traverser.Admin

Prepare the traverser for migration across a JVM boundary.

Specified by:

detach in interface Traverser.Admin<T>

Returns:

The deflated traverser

attach

public T attach(Function<Attachable<T>,T> method)

Description copied from interface: Traverser.Admin

Regenerate the detached traverser given its location at a particular vertex.

Specified by:

attach in interface Attachable<T>

Specified by:

attach in interface Traverser.Admin<T>

Parameters:

method - The method by which to attach a Traverser to an vertex.

Returns:

The inflated traverser

setSideEffects

public void setSideEffects(TraversalSideEffects sideEffects)

Description copied from interface: Traverser.Admin

Set the sideEffects of the Traversal. Given that traversers can move between machines, it may be important to re-set this when the traverser crosses machine boundaries.

Specified by:

setSideEffects in interface Traverser.Admin<T>

Parameters:

sideEffects - the sideEffects of the traversal.

get

public T get()

Description copied from interface: Traverser

Get the object that the traverser is current at.

Specified by:

get in interface Attachable<T>

Specified by:

get in interface Traverser<T>

Returns:

The current object of the traverser

sack

public <S> S sack()

Description copied from interface: Traverser

Get the sack local sack object of this traverser.

Specified by:

sack in interface Traverser<T>

Type Parameters:

S - the type of the sack object

Returns:

the sack object

sack

public <S> void sack(S object)

Description copied from interface: Traverser

Set the traversers sack object to the provided value ("sack the value").

Specified by:

sack in interface Traverser<T>

Type Parameters:

S - the type of the object

Parameters:

object - the new value of the traverser's sack

merge

public void merge(Traverser.Admin<?> other)

Description copied from interface: Traverser.Admin

When two traversers are have equality with each other, then they can be merged. This method is used to merge the traversers into a single traverser. This is used for optimization where instead of enumerating all traversers, they can be counted.

Specified by:

merge in interface Traverser.Admin<T>

Parameters:

other - the other traverser to merge into this traverser. Once merged, the other can be garbage collected.

path

public Path path()

Description copied from interface: Traverser

Get the current path of the traverser.

Specified by:

path in interface Traverser<T>

Returns:

The path of the traverser

loops

public int loops()

Description copied from interface: Traverser

Return the number of times the traverser has gone through a looping section of a traversal.

Specified by:

loops in interface Traverser<T>

Returns:

The number of times the traverser has gone through a loop

loops

public int loops(String loopName)

Description copied from interface: Traverser

Return the number of times the traverser has gone through the named looping section of a traversal.

Specified by:

loops in interface Traverser<T>

Parameters:

loopName - the name applied to the loop or null for the containing loop

Returns:

The number of times the traverser has gone through a loop

bulk

public long bulk()

Description copied from interface: Traverser

A traverser may represent a grouping of traversers to allow for more efficient data propagation.

Specified by:

bulk in interface Traverser<T>

Returns:

the number of traversers represented in this traverser.

getSideEffects

public TraversalSideEffects getSideEffects()

Description copied from interface: Traverser.Admin

Get the sideEffects associated with the traversal of the traverser.

Specified by:

getSideEffects in interface Traverser.Admin<T>

Returns:

the traversal sideEffects of the traverser

getTags

public Set<String> getTags()

Description copied from interface: Traverser.Admin

Get the tags associated with the traverser. Tags are used to categorize historic behavior of a traverser. The returned set is mutable.

Specified by:

getTags in interface Traverser.Admin<T>

Returns:

the set of tags associated with the traverser.

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object object)

Overrides:

equals in class Object

clone

public EmptyTraverser<T> clone()

Description copied from interface: Traverser

Traverser cloning is important when splitting a traverser at a bifurcation point in a traversal.

Specified by:

clone in interface Traverser<T>

Overrides:

clone in class Object