Combine.Globally (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 Combine.Globally<InputT,OutputT>

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.PTransform<PCollection<InputT>,PCollection<OutputT>>
  • • com.google.cloud.dataflow.sdk.transforms.Combine.Globally<InputT,OutputT>

• Type Parameters:

  InputT - type of input values

  OutputT - type of output values

  All Implemented Interfaces:

  HasDisplayData, Serializable

  Enclosing class:

  Combine

  ---

  
  

  public static class Combine.Globally<InputT,OutputT>
  extends PTransform<PCollection<InputT>,PCollection<OutputT>>

  Combine.Globally<InputT, OutputT> takes a PCollection<InputT> and returns a PCollection<OutputT> whose elements are the result of combining all the elements in each window of the input PCollection, using a specified CombineFn<InputT, AccumT, OutputT>. 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<Integer> pc = ...;
   PCollection<Integer> sum = pc.apply(
       Combine.globally(new Sum.SumIntegerFn()));
    

  Combining can happen in parallel, with different subsets of the input PCollection being combined separately, and their intermediate results combined further, in an arbitrary tree reduction pattern, until a single result value is produced.

  If the input PCollection is windowed into GlobalWindows, a default value in the GlobalWindow will be output if the input PCollection is empty. To use this with inputs with other windowing, either withoutDefaults() or asSingletonView() must be called, as the default value cannot be automatically assigned to any single window.

  By default, the Coder of the output PValue<OutputT> is inferred from the concrete type of the CombineFn<InputT, AccumT, OutputT>'s output type OutputT.

  See also Combine.perKey(com.google.cloud.dataflow.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>)/Combine.PerKey and Combine.groupedValues(com.google.cloud.dataflow.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>)/Combine.GroupedValues, which are useful for combining values associated with each key in a PCollection of KVs.

  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<OutputT>	apply(PCollection<InputT> input) Applies this PTransform on the given InputT, and returns its Output.
    Combine.GloballyAsSingletonView<InputT,OutputT>	asSingletonView() Returns a PTransform that produces a PCollectionView whose elements are the result of combining elements per-window in the input PCollection.
    Combine.Globally<InputT,OutputT>	named(String name) Return a new Globally transform that's like this transform but with the specified name.
    void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
    Combine.Globally<InputT,OutputT>	withFanout(int fanout) Returns a PTransform identical to this, but that uses an intermediate node to combine parts of the data to reduce load on the final global combine step.
    Combine.Globally<InputT,OutputT>	withoutDefaults() Returns a PTransform identical to this, but that does not attempt to provide a default value in the case of empty input.
    Combine.Globally<InputT,OutputT>	withSideInputs(Iterable<? extends PCollectionView<?>> sideInputs) Returns a PTransform identical to this, but with the specified side inputs to use in CombineWithContext.CombineFnWithContext.

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

      getDefaultOutputCoder, 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

    • named

      public Combine.Globally<InputT,OutputT> named(String name)

      Return a new Globally transform that's like this transform but with the specified name. Does not modify this transform.

    • asSingletonView

      public Combine.GloballyAsSingletonView<InputT,OutputT> asSingletonView()

      Returns a PTransform that produces a PCollectionView whose elements are the result of combining elements per-window in the input PCollection. If a value is requested from the view for a window that is not present, the result of applying the CombineFn to an empty input set will be returned.

    • withoutDefaults

      public Combine.Globally<InputT,OutputT> withoutDefaults()

      Returns a PTransform identical to this, but that does not attempt to provide a default value in the case of empty input. Required when the input is not globally windowed and the output is not being used as a side input.

    • withFanout

      public Combine.Globally<InputT,OutputT> withFanout(int fanout)

      Returns a PTransform identical to this, but that uses an intermediate node to combine parts of the data to reduce load on the final global combine step.

      The fanout parameter determines the number of intermediate keys that will be used.

    • withSideInputs

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

      Returns a PTransform identical to this, but with the specified side inputs to use in CombineWithContext.CombineFnWithContext.

    • apply

      public PCollection<OutputT> apply(PCollection<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<InputT>,PCollection<OutputT>>

    • 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<InputT>,PCollection<OutputT>>

      Parameters:

      builder - The builder to populate with display data.

      See Also:

      HasDisplayData