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

Class SelectStep<S,E>

java.lang.Object

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

org.apache.tinkerpop.gremlin.process.traversal.step.map.MapStep<S,Map<String,E>>

org.apache.tinkerpop.gremlin.process.traversal.step.map.SelectStep<S,E>

All Implemented Interfaces:

Serializable, AutoCloseable, Cloneable, Iterator<Traverser.Admin<Map<String,E>>>, Step<S,Map<String,E>>, ByModulating, PathProcessor, PopContaining, Scoping, TraversalParent

public final class SelectStep<S,E>
extends MapStep<S,Map<String,E>>
implements Scoping, TraversalParent, PathProcessor, ByModulating

Author:

Marko A. Rodriguez (http://markorodriguez.com), Stephen Mallette (http://stephen.genoprime.com)

See Also:

• Serialized Form

Nested Class Summary

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

PathProcessor.ElementRequirement

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

PopContaining.PopInstruction

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

Scoping.KeyNotFoundException, Scoping.Variable

Field Summary

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
SelectStep(Traversal.Admin traversal, Pop pop, String... selectKeys)

Method Summary

Modifier and Type	Method	Description
SelectStep<S,E>	clone()	Cloning is used to duplicate steps for the purpose of traversal optimization and OLTP replication.
Map<String,Traversal.Admin<Object,E>>	getByTraversals()
Set<String>	getKeepLabels()
List<Traversal.Admin<Object,E>>	getLocalChildren()	Gets a list of all "local" child traversals for this step.
Pop	getPop()
HashSet<PopContaining.PopInstruction>	getPopInstructions()	Used to get PopInstruction of a Step that implements Scoping.
Set<TraverserRequirement>	getRequirements()	Provide the necessary TraverserRequirement that must be met by the traverser in order for the step to function properly.
Set<String>	getScopeKeys()	Get the labels that this scoping step will access during the traversal
List<String>	getSelectKeys()	Get the keys for this SelectStep.
int	hashCode()
void	modulateBy(Traversal.Admin<?,?> selectTraversal)
protected Traverser.Admin<Map<String,E>>	processNextStart()
void	replaceLocalChild(Traversal.Admin<?,?> oldTraversal, Traversal.Admin<?,?> newTraversal)
void	reset()	Reset the state of the step such that it has no incoming starts.
void	setKeepLabels(Set<String> keepLabels)
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.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 java.util.Iterator

forEachRemaining, remove

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

getMaxRequirement

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

getNullableScopeValue, getSafeScopeValue, getScopeValue

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, getSelfAndChildRequirements, integrateChild, removeGlobalChild, removeLocalChild

Constructor Details

SelectStep

public SelectStep(Traversal.Admin traversal,
 Pop pop,
 String... selectKeys)

Method Details

processNextStart

protected Traverser.Admin<Map<String,E>> processNextStart()
                                                   throws NoSuchElementException

Specified by:

processNextStart in class AbstractStep<S,Map<String,E>>

Throws:

NoSuchElementException

reset

public void reset()

Description copied from interface: Step

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.

Specified by:

reset in interface Step<S,E>

Overrides:

reset in class AbstractStep<S,Map<String,E>>

toString

public String toString()

Overrides:

toString in class AbstractStep<S,Map<String,E>>

clone

public SelectStep<S,E> 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,E>

Overrides:

clone in class AbstractStep<S,Map<String,E>>

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,E>

Overrides:

setTraversal in class AbstractStep<S,Map<String,E>>

Parameters:

parentTraversal - the new traversal for this step

hashCode

public int hashCode()

Overrides:

hashCode in class AbstractStep<S,Map<String,E>>

getLocalChildren

public List<Traversal.Admin<Object,E>> 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

modulateBy

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

Specified by:

modulateBy in interface ByModulating

replaceLocalChild

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

Specified by:

replaceLocalChild 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,E>

Returns:

the set of requirements

getScopeKeys

public Set<String> getScopeKeys()

Description copied from interface: Scoping

Get the labels that this scoping step will access during the traversal

Specified by:

getScopeKeys in interface Scoping

Returns:

the accessed labels of the scoping step

getPopInstructions

public HashSet<PopContaining.PopInstruction> getPopInstructions()

Description copied from interface: Scoping

Used to get PopInstruction of a Step that implements Scoping. PopInstruction includes the labels it needs, and the pop type for each label.

Specified by:

getPopInstructions in interface PopContaining

Specified by:

getPopInstructions in interface Scoping

Specified by:

getPopInstructions in interface TraversalParent

Returns:

A Set of PopContaining.PopInstruction values which contain the label and Pop value

getSelectKeys

public List<String> getSelectKeys()

Get the keys for this SelectStep. Unlike getScopeKeys(), this returns a list possibly with a duplicate key. This guarantees to return the keys in the same order as passed in. TODO: getScopeKeys should return order-aware data structure instead of HashSet so that graph providers can get the keys in the order passed in a query, and can associate them with by-traversals in a correct sequence.

getByTraversals

public Map<String,Traversal.Admin<Object,E>> getByTraversals()

getPop

public Pop getPop()

setKeepLabels

public void setKeepLabels(Set<String> keepLabels)

Specified by:

setKeepLabels in interface PathProcessor

getKeepLabels

public Set<String> getKeepLabels()

Specified by:

getKeepLabels in interface PathProcessor