Package org.apache.beam.sdk.transforms

Class ApproximateUnique.ApproximateUniqueCombineFn<T>

java.lang.Object

org.apache.beam.sdk.transforms.Combine.CombineFn<T,ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique,Long>

org.apache.beam.sdk.transforms.ApproximateUnique.ApproximateUniqueCombineFn<T>

Type Parameters:

T - the type of the values being combined

All Implemented Interfaces:

Serializable, CombineFnBase.GlobalCombineFn<T,ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique,Long>, HasDisplayData

Enclosing class:

ApproximateUnique

public static class ApproximateUnique.ApproximateUniqueCombineFn<T>
extends Combine.CombineFn<T,ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique,Long>

CombineFn that computes an estimate of the number of distinct values that were combined.

Hashes input elements, computes the top sampleSize hash values, and uses those to extrapolate the size of the entire set of hash values by assuming the rest of the hash values are as densely distributed as the top sampleSize.

Used to implement ApproximatUnique.globally(...) and ApproximatUnique.perKey(...).

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique	A heap utility class to efficiently track the largest added elements.

Constructor Summary

Constructors

Constructor	Description
ApproximateUniqueCombineFn(long sampleSize, Coder<T> coder)

Method Summary

Modifier and Type	Method	Description
ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique	addInput(ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique heap, T input)	Adds the given input value to the given accumulator, returning the new accumulator value.
ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique	createAccumulator()	Returns a new, mutable accumulator value, representing the accumulation of zero input values.
Long	extractOutput(ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique heap)	Returns the output value that is the result of combining all the input values represented by the given accumulator.
TypeVariable<?>	getAccumTVariable()	Returns the TypeVariable of AccumT.
Coder<ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique>	getAccumulatorCoder(CoderRegistry registry, Coder<T> inputCoder)	Returns the Coder to use for accumulator AccumT values, or null if it is not able to be inferred.
Coder<Long>	getDefaultOutputCoder(CoderRegistry registry, Coder<T> inputCoder)	Returns the Coder to use by default for output OutputT values, or null if it is not able to be inferred.
String	getIncompatibleGlobalWindowErrorMessage()	Returns the error message for not supported default values in Combine.globally().
TypeVariable<?>	getInputTVariable()	Returns the TypeVariable of InputT.
TypeVariable<?>	getOutputTVariable()	Returns the TypeVariable of OutputT.
ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique	mergeAccumulators(Iterable<ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique> heaps)	Returns an accumulator representing the accumulation of all the input values accumulated in the merging accumulators.
void	populateDisplayData(DisplayData.Builder builder)	Register display data for the given transform or component.

Methods inherited from class org.apache.beam.sdk.transforms.Combine.CombineFn

apply, compact, defaultValue, getInputType, getOutputType

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ApproximateUniqueCombineFn

public ApproximateUniqueCombineFn(long sampleSize,
 Coder<T> coder)

Method Details

createAccumulator

public ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique createAccumulator()

Description copied from class: Combine.CombineFn

Returns a new, mutable accumulator value, representing the accumulation of zero input values.

Specified by:

createAccumulator in class Combine.CombineFn<T,ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique,Long>

addInput

public ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique addInput(ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique heap,
 T input)

Description copied from class: Combine.CombineFn

Adds the given input value to the given accumulator, returning the new accumulator value.

Specified by:

addInput in class Combine.CombineFn<T,ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique,Long>

Parameters:

heap - may be modified and returned for efficiency

input - should not be mutated

mergeAccumulators

public ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique mergeAccumulators(Iterable<ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique> heaps)

Description copied from class: Combine.CombineFn

Returns an accumulator representing the accumulation of all the input values accumulated in the merging accumulators.

Specified by:

mergeAccumulators in class Combine.CombineFn<T,ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique,Long>

Parameters:

heaps - only the first accumulator may be modified and returned for efficiency; the other accumulators should not be mutated, because they may be shared with other code and mutating them could lead to incorrect results or data corruption.

extractOutput

public Long extractOutput(ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique heap)

Description copied from class: Combine.CombineFn

Returns the output value that is the result of combining all the input values represented by the given accumulator.

Specified by:

extractOutput in class Combine.CombineFn<T,ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique,Long>

Parameters:

heap - can be modified for efficiency

getAccumulatorCoder

public Coder<ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique> getAccumulatorCoder(CoderRegistry registry,
 Coder<T> inputCoder)

Description copied from interface: CombineFnBase.GlobalCombineFn

Returns the Coder to use for accumulator AccumT values, or null if it is not able to be inferred.

By default, uses the knowledge of the Coder being used for InputT values and the enclosing Pipeline's CoderRegistry to try to infer the Coder for AccumT values.

This is the Coder used to send data through a communication-intensive shuffle step, so a compact and efficient representation may have significant performance benefits.

Specified by:

getAccumulatorCoder in interface CombineFnBase.GlobalCombineFn<T,ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique,Long>

getDefaultOutputCoder

public Coder<Long> getDefaultOutputCoder(CoderRegistry registry,
 Coder<T> inputCoder)
                                  throws CannotProvideCoderException

Description copied from interface: CombineFnBase.GlobalCombineFn

Returns the Coder to use by default for output OutputT values, or null if it is not able to be inferred.

By default, uses the knowledge of the Coder being used for input InputT values and the enclosing Pipeline's CoderRegistry to try to infer the Coder for OutputT values.

Specified by:

getDefaultOutputCoder in interface CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>

Throws:

CannotProvideCoderException

getIncompatibleGlobalWindowErrorMessage

public String getIncompatibleGlobalWindowErrorMessage()

Description copied from interface: CombineFnBase.GlobalCombineFn

Returns the error message for not supported default values in Combine.globally().

Specified by:

getIncompatibleGlobalWindowErrorMessage in interface CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>

getInputTVariable

public TypeVariable<?> getInputTVariable()

Returns the TypeVariable of InputT.

getAccumTVariable

public TypeVariable<?> getAccumTVariable()

Returns the TypeVariable of AccumT.

getOutputTVariable

public TypeVariable<?> getOutputTVariable()

Returns the TypeVariable of OutputT.

populateDisplayData

public void populateDisplayData(DisplayData.Builder builder)

Register display data for the given transform or component.

populateDisplayData(DisplayData.Builder) is invoked by Pipeline runners to collect display data via DisplayData.from(HasDisplayData). Implementations may call super.populateDisplayData(builder) in order to register display data in the current namespace, but should otherwise use subcomponent.populateDisplayData(builder) to use the namespace of the subcomponent.

By default, does not register any display data. Implementors may override this method to provide their own display data.

Specified by:

populateDisplayData in interface HasDisplayData

Parameters:

builder - The builder to populate with display data.

See Also:

• HasDisplayData