Keys (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.

com.google.cloud.dataflow.sdk.transforms

Class Keys<K>

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.PTransform<PCollection<? extends KV<K,?>>,PCollection<K>>
  • • com.google.cloud.dataflow.sdk.transforms.Keys<K>

• Type Parameters:

  K - the type of the keys in the input PCollection, and the type of the elements in the output PCollection

  All Implemented Interfaces:

  HasDisplayData, Serializable

  ---

  
  

  public class Keys<K>
  extends PTransform<PCollection<? extends KV<K,?>>,PCollection<K>>

  Keys<K> takes a PCollection of KV<K, V>s and returns a PCollection<K> of the keys.

  Example of use:

   
   PCollection<KV<String, Long>> wordCounts = ...;
   PCollection<String> words = wordCounts.apply(Keys.<String>create());
    

  Each output element has the same timestamp and is in the same windows as its corresponding input element, and the output PCollection has the same WindowFn associated with it as the input.

  See also Values.

  See Also:

  Serialized Form

• • Field Summary

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

      name

  • Method Summary

    All Methods Static Methods Instance Methods Concrete Methods 

    Modifier and Type	Method and Description
    PCollection<K>	apply(PCollection<? extends KV<K,?>> in) Applies this PTransform on the given InputT, and returns its Output.
    static <K> Keys<K>	create() Returns a Keys<K> 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

• • Method Detail

    • create

      public static <K> Keys<K> create()

      Returns a Keys<K> PTransform.

      Type Parameters:

      K - the type of the keys in the input PCollection, and the type of the elements in the output PCollection

    • apply

      public PCollection<K> apply(PCollection<? extends KV<K,?>> 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<? extends KV<K,?>>,PCollection<K>>