Class ReducingBarrierStep<S,​E>

    • Field Detail


        public static final Object NON_EMITTING_SEED
        A seed value not to be emitted from the ReducingBarrierStep helping with flow control within this step.
      • seedSupplier

        protected Supplier<E> seedSupplier
        If the seedSupplier is null then the default behavior is to generate the seed from the starts. This supplier must be callable as a constant and not rely on state from the class. Prefer overriding generateSeedFromStarts() otherwise.
      • hasProcessedOnce

        protected boolean hasProcessedOnce
    • Constructor Detail

      • ReducingBarrierStep

        public ReducingBarrierStep​(Traversal.Admin traversal)
    • Method Detail

      • setSeedSupplier

        public void setSeedSupplier​(Supplier<E> seedSupplier)
      • generateSeedFromStarts

        protected E generateSeedFromStarts()
        If the seedSupplier is null then this method is called.
      • projectTraverser

        public abstract E projectTraverser​(Traverser.Admin<S> traverser)
      • setReducingBiOperator

        public void setReducingBiOperator​(BinaryOperator<E> reducingBiOperator)
      • 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>
        reset in class AbstractStep<S,​E>
      • done

        public void done()
        Description copied from interface: Barrier
        A way to hard set that the barrier is complete. This is necessary when parallel barriers don't all have barriers and need hard resetting. The default implementation does nothing.
        Specified by:
        done in interface Barrier<S>
      • processAllStarts

        public void processAllStarts()
        Description copied from interface: Barrier
        Process all left traversers by do not yield the resultant output. This method is useful for steps like ReducingBarrierStep, where traversers can be processed "on the fly" and thus, reduce memory consumption.
        Specified by:
        processAllStarts in interface Barrier<S>
      • hasNextBarrier

        public boolean hasNextBarrier()
        Description copied from interface: Barrier
        Whether or not the step has an accessible barrier.
        Specified by:
        hasNextBarrier in interface Barrier<S>
        whether a barrier exists or not
      • nextBarrier

        public E nextBarrier()
        Description copied from interface: Barrier
        Get the next barrier within this step. Barriers from parallel steps can be the be merged to create a single step with merge barriers.
        Specified by:
        nextBarrier in interface Barrier<S>
        the next barrier of the step
      • addBarrier

        public void addBarrier​(E barrier)
        Description copied from interface: Barrier
        Add a barrier to the step. This typically happens when multiple parallel barriers need to become one barrier at a single step.
        Specified by:
        addBarrier in interface Barrier<S>
        barrier - the barrier to merge in
      • clone

        public ReducingBarrierStep<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>
        clone in class AbstractStep<S,​E>
        The cloned step