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 Details

    • 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

    • clearLabels

      void clearLabels()
      Removes all labels on the 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