Partition (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 Partition<T>

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

• Type Parameters:

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

  All Implemented Interfaces:

  HasDisplayData, Serializable

  ---

  
  

  public class Partition<T>
  extends PTransform<PCollection<T>,PCollectionList<T>>

  Partition takes a PCollection<T> and a PartitionFn, uses the PartitionFn to split the elements of the input PCollection into N partitions, and returns a PCollectionList<T> that bundles N PCollection<T>s containing the split elements.

  Example of use:

   
   PCollection<Student> students = ...;
   // Split students up into 10 partitions, by percentile:
   PCollectionList<Student> studentsByPercentile =
       students.apply(Partition.of(10, new PartitionFn<Student>() {
           public int partitionFor(Student student, int numPartitions) {
               return student.getPercentile()  // 0..99
                    * numPartitions / 100;
           }}))
   for (int i = 0; i < 10; i++) {
     PCollection<Student> partition = studentsByPercentile.get(i);
     ...
   }
    

  By default, the Coder of each of the PCollections in the output PCollectionList is the same as the Coder of the input PCollection.

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

  See Also:

  Serialized Form

• • Nested Class Summary

    Nested Classes 

    Modifier and Type	Class and Description
    static interface	Partition.PartitionFn<T> A function object that chooses an output partition for an element.

  • 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
    PCollectionList<T>	apply(PCollection<T> in) Applies this PTransform on the given InputT, and returns its Output.
    static <T> Partition<T>	of(int numPartitions, Partition.PartitionFn<? super T> partitionFn) Returns a new Partition PTransform that divides its input PCollection into the given number of partitions, using the given partitioning function.
    void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.

    • 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

    • of

      public static <T> Partition<T> of(int numPartitions,
                                        Partition.PartitionFn<? super T> partitionFn)

      Returns a new Partition PTransform that divides its input PCollection into the given number of partitions, using the given partitioning function.

      Parameters:

      numPartitions - the number of partitions to divide the input PCollection into

      partitionFn - the function to invoke on each element to choose its output partition

      Throws:

      IllegalArgumentException - if numPartitions <= 0

    • apply

      public PCollectionList<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>,PCollectionList<T>>

    • 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<T>,PCollectionList<T>>

      Parameters:

      builder - The builder to populate with display data.

      See Also:

      HasDisplayData