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:

  • 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 Details

    • EmptyTraverser

      protected EmptyTraverser()

  • Method Details

    • 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