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:

java.io.Serializable

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

A transform 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

Methods

Modifier and Type	Method and Description
PCollection<KV<K,CoGbkResult>>	apply(KeyedPCollectionTuple<K> input) Applies this PTransform on the given Input, 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

finishSpecifying, getCoderRegistry, getDefaultName, getDefaultOutputCoder, getDefaultOutputCoder, getInput, getKindString, getName, getOutput, getPipeline, setName, setPipeline, toString, withName

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 Input, 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<Input, Output>, Input).

Overrides:

apply in class PTransform<KeyedPCollectionTuple<K>,PCollection<KV<K,CoGbkResult>>>