Class ReducingBarrierStep<S,E>
- java.lang.Object
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- org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep<S,E>
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- org.apache.tinkerpop.gremlin.process.traversal.step.util.ReducingBarrierStep<S,E>
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- All Implemented Interfaces:
Serializable
,Cloneable
,Iterator<Traverser.Admin<E>>
,Step<S,E>
,Barrier<E>
,Generating<E,E>
,MemoryComputing<E>
- Direct Known Subclasses:
CountGlobalStep
,FoldStep
,GroupCountStep
,GroupStep
,MaxGlobalStep
,MeanGlobalStep
,MinGlobalStep
,SumGlobalStep
,TreeStep
public abstract class ReducingBarrierStep<S,E> extends AbstractStep<S,E> implements Barrier<E>, Generating<E,E>
- Author:
- Marko A. Rodriguez (http://markorodriguez.com)
- See Also:
- Serialized Form
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
ReducingBarrierStep.NonEmittingSeed
A class that represents a value that is not be to be emitted which helps with flow control internal to the class and is serializable in Gryo for use in OLAP.
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Field Summary
Fields Modifier and Type Field Description protected boolean
hasProcessedOnce
static Object
NON_EMITTING_SEED
A seed value not to be emitted from theReducingBarrierStep
helping with flow control within this step.protected BinaryOperator<E>
reducingBiOperator
protected Supplier<E>
seedSupplier
If theseedSupplier
isnull
then the default behavior is to generate the seed from the starts.-
Fields inherited from class org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep
id, labels, nextEnd, nextStep, previousStep, starts, traversal, traverserStepIdAndLabelsSetByChild
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Constructor Summary
Constructors Constructor Description ReducingBarrierStep(Traversal.Admin traversal)
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description void
addBarrier(E barrier)
Add a barrier to the step.ReducingBarrierStep<S,E>
clone()
Cloning is used to duplicate steps for the purpose of traversal optimization and OLTP replication.void
done()
A way to hard set that the barrier is complete.protected E
generateSeedFromStarts()
If theseedSupplier
isnull
then this method is called.BinaryOperator<E>
getBiOperator()
MemoryComputeKey<E>
getMemoryComputeKey()
TheMemoryComputeKey
that will be used by this step.Supplier<E>
getSeedSupplier()
Gets the provided seed supplier or providesgenerateSeedFromStarts()
.boolean
hasNextBarrier()
Whether or not the step has an accessible barrier.E
nextBarrier()
Get the next barrier within this step.void
processAllStarts()
Process all left traversers by do not yield the resultant output.Traverser.Admin<E>
processNextStart()
abstract E
projectTraverser(Traverser.Admin<S> traverser)
void
reset()
Reset the state of the step such that it has no incoming starts.void
setReducingBiOperator(BinaryOperator<E> reducingBiOperator)
void
setSeedSupplier(Supplier<E> seedSupplier)
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Methods inherited from class org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep
addLabel, addStart, addStarts, clearLabels, equals, getId, getLabels, getNextStep, getPreviousStep, getStarts, getTraversal, hashCode, hasNext, hasStarts, isTraverserStepIdAndLabelsSetByChild, next, prepareTraversalForNextStep, removeLabel, setId, setNextStep, setPreviousStep, setTraversal, toString
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Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface org.apache.tinkerpop.gremlin.process.traversal.step.Generating
generateFinalResult
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Methods inherited from interface java.util.Iterator
forEachRemaining, remove
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Methods inherited from interface org.apache.tinkerpop.gremlin.process.traversal.Step
equals, getRequirements
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Field Detail
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NON_EMITTING_SEED
public static final Object NON_EMITTING_SEED
A seed value not to be emitted from theReducingBarrierStep
helping with flow control within this step.
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seedSupplier
protected Supplier<E> seedSupplier
If theseedSupplier
isnull
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 overridinggenerateSeedFromStarts()
otherwise.
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reducingBiOperator
protected BinaryOperator<E> reducingBiOperator
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hasProcessedOnce
protected boolean hasProcessedOnce
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Constructor Detail
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ReducingBarrierStep
public ReducingBarrierStep(Traversal.Admin traversal)
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Method Detail
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getSeedSupplier
public Supplier<E> getSeedSupplier()
Gets the provided seed supplier or providesgenerateSeedFromStarts()
.
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generateSeedFromStarts
protected E generateSeedFromStarts()
If theseedSupplier
isnull
then this method is called.
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projectTraverser
public abstract E projectTraverser(Traverser.Admin<S> traverser)
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setReducingBiOperator
public void setReducingBiOperator(BinaryOperator<E> reducingBiOperator)
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getBiOperator
public BinaryOperator<E> getBiOperator()
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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.
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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.
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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 likeReducingBarrierStep
, where traversers can be processed "on the fly" and thus, reduce memory consumption.- Specified by:
processAllStarts
in interfaceBarrier<S>
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hasNextBarrier
public boolean hasNextBarrier()
Description copied from interface:Barrier
Whether or not the step has an accessible barrier.- Specified by:
hasNextBarrier
in interfaceBarrier<S>
- Returns:
- whether a barrier exists or not
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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 interfaceBarrier<S>
- Returns:
- the next barrier of the step
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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 interfaceBarrier<S>
- Parameters:
barrier
- the barrier to merge in
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processNextStart
public Traverser.Admin<E> processNextStart()
- Specified by:
processNextStart
in classAbstractStep<S,E>
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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 whenStep.reset()
is called. Moreover, the previous and next steps should be set toEmptyStep
.
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getMemoryComputeKey
public MemoryComputeKey<E> getMemoryComputeKey()
Description copied from interface:MemoryComputing
TheMemoryComputeKey
that will be used by this step.- Specified by:
getMemoryComputeKey
in interfaceMemoryComputing<S>
- Returns:
- the MemoryComputeKey to use
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