RemoveDuplicates (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. See Migrating from Dataflow SDK 1.x for Java for migration guidance.

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

com.google.cloud.dataflow.sdk.transforms

Class RemoveDuplicates<T>

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.PTransform<PCollection<T>,PCollection<T>>
  • • com.google.cloud.dataflow.sdk.transforms.RemoveDuplicates<T>

• Type Parameters:

  T - the type of the elements of the input and output PCollections

  All Implemented Interfaces:

  HasDisplayData, Serializable

  ---

  
  

  public class RemoveDuplicates<T>
  extends PTransform<PCollection<T>,PCollection<T>>

  RemoveDuplicates<T> takes a PCollection<T> and returns a PCollection<T> that has all the elements of the input but with duplicate elements removed such that each element is unique within each window.

  Two values of type T are compared for equality not by regular Java Object.equals(java.lang.Object), but instead by first encoding each of the elements using the PCollection's Coder, and then comparing the encoded bytes. This admits efficient parallel evaluation.

  Optionally, a function may be provided that maps each element to a representative value. In this case, two elements will be considered duplicates if they have equal representative values, with equality being determined as above.

  By default, the Coder of the output PCollection is the same as the Coder of the input PCollection.

  Each output element is in the same window as its corresponding input element, and has the timestamp of the end of that window. The output PCollection has the same WindowFn as the input.

  Does not preserve any order the input PCollection might have had.

  Example of use:

   
   PCollection<String> words = ...;
   PCollection<String> uniqueWords =
       words.apply(RemoveDuplicates.<String>create());
    

  See Also:

  Serialized Form

• • Nested Class Summary

    Nested Classes 

    Modifier and Type	Class and Description
    static class	RemoveDuplicates.WithRepresentativeValues<T,IdT> A RemoveDuplicates PTransform that uses a SerializableFunction to obtain a representative value for each input element.

  • Field Summary

    • Fields inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform

      name

  • Constructor Summary

    Constructors 

    Constructor and Description
    RemoveDuplicates()

  • Method Summary

    All Methods Static Methods Instance Methods Concrete Methods 

    Modifier and Type	Method and Description
    PCollection<T>	apply(PCollection<T> in) Applies this PTransform on the given InputT, and returns its Output.
    static <T> RemoveDuplicates<T>	create() Returns a RemoveDuplicates<T> PTransform.
    static <T,IdT> RemoveDuplicates.WithRepresentativeValues<T,IdT>	withRepresentativeValueFn(SerializableFunction<T,IdT> fn) Returns a RemoveDuplicates<T, IdT> PTransform.

    • Methods inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform

      getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, populateDisplayData, toString, validate

    • Methods inherited from class java.lang.Object

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

• • Constructor Detail

    • RemoveDuplicates

      public RemoveDuplicates()

  • Method Detail

    • create

      public static <T> RemoveDuplicates<T> create()

      Returns a RemoveDuplicates<T> PTransform.

      Type Parameters:

      T - the type of the elements of the input and output PCollections

    • withRepresentativeValueFn

      public static <T,IdT> RemoveDuplicates.WithRepresentativeValues<T,IdT> withRepresentativeValueFn(SerializableFunction<T,IdT> fn)

      Returns a RemoveDuplicates<T, IdT> PTransform.

      Type Parameters:

      T - the type of the elements of the input and output PCollections

      IdT - the type of the representative value used to dedup

    • apply

      public PCollection<T> apply(PCollection<T> in)

      Description copied from class: PTransform
      Applies this PTransform on the given InputT, and returns its Output.

      Composite transforms, which are defined in terms of other transforms, should return the output of one of the composed transforms. Non-composite transforms, which do not apply any transforms internally, should return a new unbound output and register evaluators (via backend-specific registration methods).

      The default implementation throws an exception. A derived class must either implement apply, or else each runner must supply a custom implementation via PipelineRunner.apply(com.google.cloud.dataflow.sdk.transforms.PTransform<InputT, OutputT>, InputT).

      Overrides:

      apply in class PTransform<PCollection<T>,PCollection<T>>