Combine.GroupedValues (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 Combine.GroupedValues<K,InputT,OutputT>

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.PTransform<PCollection<? extends KV<K,? extends Iterable<InputT>>>,PCollection<KV<K,OutputT>>>
  • • com.google.cloud.dataflow.sdk.transforms.Combine.GroupedValues<K,InputT,OutputT>

• Type Parameters:

  K - type of input and output keys

  InputT - type of input values

  OutputT - type of output values

  All Implemented Interfaces:

  HasDisplayData, Serializable

  Enclosing class:

  Combine

  ---

  
  

  public static class Combine.GroupedValues<K,InputT,OutputT>
  extends PTransform<PCollection<? extends KV<K,? extends Iterable<InputT>>>,PCollection<KV<K,OutputT>>>

  GroupedValues<K, InputT, OutputT> takes a PCollection<KV<K, Iterable<InputT>>>, such as the result of GroupByKey, applies a specified KeyedCombineFn<K, InputT, AccumT, OutputT> to each of the input KV<K, Iterable<InputT>> elements to produce a combined output KV<K, OutputT> element, and returns a PCollection<KV<K, OutputT>> containing all the combined output elements. It is common for InputT == OutputT, but not required. Common combining functions include sums, mins, maxes, and averages of numbers, conjunctions and disjunctions of booleans, statistical aggregations, etc.

  Example of use:

   
   PCollection<KV<String, Integer>> pc = ...;
   PCollection<KV<String, Iterable<Integer>>> groupedByKey = pc.apply(
       new GroupByKey<String, Integer>());
   PCollection<KV<String, Integer>> sumByKey = groupedByKey.apply(
       Combine.<String, Integer>groupedValues(
           new Sum.SumIntegerFn()));
    

  See also Combine.perKey(com.google.cloud.dataflow.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>)/Combine.PerKey, which captures the common pattern of "combining by key" in a single easy-to-use PTransform.

  Combining for different keys can happen in parallel. Moreover, combining of the Iterable<InputT> values associated a single key can happen in parallel, with different subsets of the values being combined separately, and their intermediate results combined further, in an arbitrary tree reduction pattern, until a single result value is produced for each key.

  By default, the Coder of the keys of the output PCollection<KV<K, OutputT>> is that of the keys of the input PCollection<KV<K, InputT>>, and the Coder of the values of the output PCollection<KV<K, OutputT>> is inferred from the concrete type of the KeyedCombineFn<K, InputT, AccumT, OutputT>'s output type OutputT.

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

  See also Combine.globally(com.google.cloud.dataflow.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>)/Combine.Globally, which combines all the values in a PCollection into a single value in a PCollection.

  See Also:

  Serialized Form

• • Field Summary

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

      name

  • Method Summary

    All Methods Instance Methods Concrete Methods 

    Modifier and Type	Method and Description
    PCollection<KV<K,OutputT>>	apply(PCollection<? extends KV<K,? extends Iterable<InputT>>> input) Applies this PTransform on the given InputT, and returns its Output.
    com.google.cloud.dataflow.sdk.util.AppliedCombineFn<? super K,? super InputT,?,OutputT>	getAppliedFn(CoderRegistry registry, Coder<? extends KV<K,? extends Iterable<InputT>>> inputCoder, com.google.cloud.dataflow.sdk.util.WindowingStrategy<?,?> windowingStrategy) Returns the Combine.CombineFn bound to its coders.
    Coder<KV<K,OutputT>>	getDefaultOutputCoder(PCollection<? extends KV<K,? extends Iterable<InputT>>> input) Returns the default Coder to use for the output of this single-output PTransform when applied to the given input.
    CombineFnBase.PerKeyCombineFn<? super K,? super InputT,?,OutputT>	getFn() Returns the KeyedCombineFn used by this Combine operation.
    List<PCollectionView<?>>	getSideInputs()
    void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
    Combine.GroupedValues<K,InputT,OutputT>	withSideInputs(Iterable<? extends PCollectionView<?>> sideInputs)

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

      getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, toString, validate

    • Methods inherited from class java.lang.Object

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

• • Method Detail

    • withSideInputs

      public Combine.GroupedValues<K,InputT,OutputT> withSideInputs(Iterable<? extends PCollectionView<?>> sideInputs)

    • getFn

      public CombineFnBase.PerKeyCombineFn<? super K,? super InputT,?,OutputT> getFn()

      Returns the KeyedCombineFn used by this Combine operation.

    • getSideInputs

      public List<PCollectionView<?>> getSideInputs()

    • apply

      public PCollection<KV<K,OutputT>> apply(PCollection<? extends KV<K,? extends Iterable<InputT>>> 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<? extends KV<K,? extends Iterable<InputT>>>,PCollection<KV<K,OutputT>>>

    • getAppliedFn

      public com.google.cloud.dataflow.sdk.util.AppliedCombineFn<? super K,? super InputT,?,OutputT> getAppliedFn(CoderRegistry registry,
                                                                                                                  Coder<? extends KV<K,? extends Iterable<InputT>>> inputCoder,
                                                                                                                  com.google.cloud.dataflow.sdk.util.WindowingStrategy<?,?> windowingStrategy)

      Returns the Combine.CombineFn bound to its coders.

      For internal use.

    • getDefaultOutputCoder

      public Coder<KV<K,OutputT>> getDefaultOutputCoder(PCollection<? extends KV<K,? extends Iterable<InputT>>> input)
                                                 throws CannotProvideCoderException

      Description copied from class: PTransform
      Returns the default Coder to use for the output of this single-output PTransform when applied to the given input.

      By default, always throws.

      Overrides:

      getDefaultOutputCoder in class PTransform<PCollection<? extends KV<K,? extends Iterable<InputT>>>,PCollection<KV<K,OutputT>>>

      Throws:

      CannotProvideCoderException - if none can be inferred.

    • populateDisplayData

      public void populateDisplayData(DisplayData.Builder builder)

      Description copied from class: PTransform
      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

      Overrides:

      populateDisplayData in class PTransform<PCollection<? extends KV<K,? extends Iterable<InputT>>>,PCollection<KV<K,OutputT>>>

      Parameters:

      builder - The builder to populate with display data.

      See Also:

      HasDisplayData