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

Interface Step<S,E>

Type Parameters:

S - The incoming object type of the step

E - The outgoing object type of the step

All Superinterfaces:

Cloneable, Iterator<Traverser.Admin<E>>, Serializable

public interface Step<S,E>
extends Iterator<Traverser.Admin<E>>, Serializable, Cloneable

A Step denotes a unit of computation within a Traversal. A step takes an incoming object and yields an outgoing object. Steps are chained together in a Traversal to yield a lazy function chain of computation.

In the constructor of a Step, never store explicit sideEffect objects in TraversalSideEffects. If a sideEffect needs to be registered with the Traversal, use SideEffects.registerSupplier().

Method Summary

Modifier and Type	Method	Description
void	addLabel(String label)	Add a label to this step.
void	addStart(Traverser.Admin<S> start)	Add a single Traverser.Admin to the step.
void	addStarts(Iterator<Traverser.Admin<S>> starts)	Add an iterator of Traverser.Admin objects of type S to the step.
Step<S,E>	clone()	Cloning is used to duplicate steps for the purpose of traversal optimization and OLTP replication.
default boolean	equals(Step other, boolean compareIds)	Compare the current step with another step.
String	getId()	Get the unique id of this step.
Set<String>	getLabels()	Get the labels of this step.
Step<E,?>	getNextStep()	Get the next step to the current step.
Step<?,S>	getPreviousStep()	Get the step prior to the current step.
default Set<org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement>	getRequirements()	Provide the necessary TraverserRequirement that must be met by the traverser in order for the step to function properly.
<A,B> Traversal.Admin<A,B>	getTraversal()	Get the Traversal.Admin that this step is contained within.
boolean	hasStarts()	Determines if starts objects are present without iterating forward.
void	removeLabel(String label)	Remove a label from this step.
void	reset()	Reset the state of the step such that it has no incoming starts.
void	setId(String id)	Get the unique id of the step.
void	setNextStep(Step<E,?> step)	Set the step that is next to the current step.
void	setPreviousStep(Step<?,S> step)	Set the step that is previous to the current step.
void	setTraversal(Traversal.Admin<?,?> traversal)	Set the Traversal that this step is contained within.

Methods inherited from interface java.util.Iterator

forEachRemaining, hasNext, next, remove

Method Detail

addStarts

void addStarts(Iterator<Traverser.Admin<S>> starts)

Add an iterator of Traverser.Admin objects of type S to the step.

Parameters:

starts - The iterator of objects to add

addStart

void addStart(Traverser.Admin<S> start)

Add a single Traverser.Admin to the step.

Parameters:

start - The traverser to add

hasStarts

boolean hasStarts()

Determines if starts objects are present without iterating forward. This function has special applicability around ReducingBarrierStep implementations where they always return true for calls to Iterator.hasNext(). Using this function gives insight to what the step itself is holding in its iterator without performing any sort of processing on the step itself.

setPreviousStep

void setPreviousStep(Step<?,S> step)

Set the step that is previous to the current step. Used for linking steps together to form a function chain.

Parameters:

step - the previous step of this step

getPreviousStep

Step<?,S> getPreviousStep()

Get the step prior to the current step.

Returns:

The previous step

setNextStep

void setNextStep(Step<E,?> step)

Set the step that is next to the current step. Used for linking steps together to form a function chain.

Parameters:

step - the next step of this step

getNextStep

Step<E,?> getNextStep()

Get the next step to the current step.

Returns:

The next step

getTraversal

<A,B> Traversal.Admin<A,B> getTraversal()

Get the Traversal.Admin that this step is contained within.

Type Parameters:

A - The incoming object type of the traversal

B - The outgoing object type of the traversal

Returns:

The traversal of this step

setTraversal

void setTraversal(Traversal.Admin<?,?> traversal)

Set the Traversal that this step is contained within.

Parameters:

traversal - the new traversal for this step

reset

void reset()

Reset the state of the step such that it has no incoming starts. Internal states are to be reset, but any sideEffect data structures are not to be recreated.

clone

Step<S,E> clone()

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 reset() is called. Moreover, the previous and next steps should be set to EmptyStep.

Returns:

The cloned step

getLabels

Set<String> getLabels()

Get the labels of this step. The labels are ordered by the order of the calls to addLabel(java.lang.String).

Returns:

the set of labels for this step

addLabel

void addLabel(String label)

Add a label to this step.

Parameters:

label - the label to add to this step

removeLabel

void removeLabel(String label)

Remove a label from this step.

Parameters:

label - the label to remove from this step

setId

void setId(String id)

Get the unique id of the step. These ids can change when strategies are applied and anonymous traversals are embedded in the parent traversal. A developer should typically not need to call this method.

Parameters:

id - the unique id of the step

getId

String getId()

Get the unique id of this step.

Returns:

the unique id of the step

getRequirements

default Set<org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement> getRequirements()

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.

Returns:

the set of requirements

equals

default boolean equals(Step other,
                       boolean compareIds)

Compare the current step with another step.

Parameters:

other - the other step

compareIds - whether to compare step IDs or not

Returns:

true if the steps are equal, otherwise false