Count.PerElement (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

Warning: Cloud Dataflow SDK 1.x for Java is unsupported as of October 16, 2018. See Migrating from Cloud 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.

com.google.cloud.dataflow.sdk.transforms

Class Count.PerElement<T>

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.PTransform<PCollection<T>,PCollection<KV<T,Long>>>
  • • com.google.cloud.dataflow.sdk.transforms.Count.PerElement<T>

• Type Parameters:

  T - the type of the elements of the input PCollection, and the type of the keys of the output PCollection

  All Implemented Interfaces:

  HasDisplayData, Serializable

  Enclosing class:

  Count

  ---

  
  

  public static class Count.PerElement<T>
  extends PTransform<PCollection<T>,PCollection<KV<T,Long>>>

  Count.PerElement<T> takes a PCollection<T> and returns a PCollection<KV<T, Long>> representing a map from each distinct element of the input PCollection to the number of times that element occurs in the input. Each key in the output PCollection is unique.

  This transform compares two values of type T by first encoding each element using the input PCollection's Coder, then comparing the encoded bytes. Because of this, the input coder must be deterministic. (See Coder.verifyDeterministic() for more detail). Performing the comparison in this manner admits efficient parallel evaluation.

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

  Example of use:

   
   PCollection<String> words = ...;
   PCollection<KV<String, Long>> wordCounts =
       words.apply(Count.<String>perElement());
    

  See Also:

  Serialized Form

• • Field Summary

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

      name

  • Constructor Summary

    Constructors 

    Constructor and Description
    PerElement()

  • Method Summary

    All Methods Instance Methods Concrete Methods 

    Modifier and Type	Method and Description
    PCollection<KV<T,Long>>	apply(PCollection<T> input) Applies this PTransform on the given InputT, and returns its Output.

    • 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

    • PerElement

      public PerElement()

  • Method Detail

    • apply

      public PCollection<KV<T,Long>> apply(PCollection<T> input)

      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<KV<T,Long>>>