ApproximateUnique.ApproximateUniqueCombineFn (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

Warning: Dataflow SDK 1.x for Java is unsupported as of October 16, 2018. After August 12, 2020, you can use unsupported SDKs temporarily while you upgrade your pipelines. For more information, see Using an unsupported SDK.

For information on migrating from the 1.x SDK, see Migrating from Dataflow SDK 1.x for Java.

Note: If you are using Cloud Dataflow SDK version 2.x, see the Apache Beam API reference documentation.

com.google.cloud.dataflow.sdk.transforms

Class ApproximateUnique.ApproximateUniqueCombineFn<T>

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.Combine.CombineFn<T,ApproximateUnique.ApproximateUniqueCombineFn.LargestUnique,Long>
  • • com.google.cloud.dataflow.sdk.transforms.ApproximateUnique.ApproximateUniqueCombineFn<T>

• Type Parameters:

  T - the type of the values being combined

  All Implemented Interfaces:

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

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

  • Constructor Summary

    Constructors 

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

  • Method Summary

    All Methods Instance Methods Concrete Methods 

    Modifier and Type	Method and 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<OutputT>	getDefaultOutputCoder(CoderRegistry registry, Coder<InputT> 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 com.google.cloud.dataflow.sdk.transforms.Combine.CombineFn

      apply, asKeyedFn, compact, defaultValue, getOutputType

    • Methods inherited from class java.lang.Object

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

• • Constructor Detail

    • ApproximateUniqueCombineFn

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

  • Method Detail

    • 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.

      For efficiency, the input accumulator may be modified and returned.

      Specified by:

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

    • 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.

      May modify any of the argument accumulators. May return a fresh accumulator, or may return one of the (modified) argument accumulators.

      Specified by:

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

    • 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>

    • 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<OutputT> getDefaultOutputCoder(CoderRegistry registry,
                                                  Coder<InputT> 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