CoGroupByKey (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.join

Class CoGroupByKey<K>

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.PTransform<KeyedPCollectionTuple<K>,PCollection<KV<K,CoGbkResult>>>
  • • com.google.cloud.dataflow.sdk.transforms.join.CoGroupByKey<K>

• Type Parameters:

  K - the type of the keys in the input and output PCollections

  All Implemented Interfaces:

  HasDisplayData, Serializable

  ---

  
  

  public class CoGroupByKey<K>
  extends PTransform<KeyedPCollectionTuple<K>,PCollection<KV<K,CoGbkResult>>>

  A PTransform that performs a CoGroupByKey on a tuple of tables. A CoGroupByKey groups results from all tables by like keys into CoGbkResults, from which the results for any specific table can be accessed by the TupleTag supplied with the initial table.

  Example of performing a CoGroupByKey followed by a ParDo that consumes the results:

  
   PCollection<KV<K, V1>> pt1 = ...;
   PCollection<KV<K, V2>> pt2 = ...;
  
   final TupleTag<V1> t1 = new TupleTag<>();
   final TupleTag<V2> t2 = new TupleTag<>();
   PCollection<KV<K, CoGbkResult>> coGbkResultCollection =
     KeyedPCollectionTuple.of(t1, pt1)
                          .and(t2, pt2)
                          .apply(CoGroupByKey.<K>create());
  
   PCollection<T> finalResultCollection =
     coGbkResultCollection.apply(ParDo.of(
       new DoFn<KV<K, CoGbkResult>, T>() {
         @Override
         public void processElement(ProcessContext c) {
           KV<K, CoGbkResult> e = c.element();
           Iterable<V1> pt1Vals = e.getValue().getAll(t1);
           V2 pt2Val = e.getValue().getOnly(t2);
            ... Do Something ....
           c.output(...some T...);
         }
       }));
  

  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<KV<K,CoGbkResult>>	apply(KeyedPCollectionTuple<K> input) Applies this PTransform on the given InputT, and returns its Output.
    static <K> CoGroupByKey<K>	create() Returns a CoGroupByKey<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> CoGroupByKey<K> create()

      Returns a CoGroupByKey<K> PTransform.

      Type Parameters:

      K - the type of the keys in the input and output PCollections

    • apply

      public PCollection<KV<K,CoGbkResult>> apply(KeyedPCollectionTuple<K> 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<KeyedPCollectionTuple<K>,PCollection<KV<K,CoGbkResult>>>