org.apache.beam.sdk.transforms.join

Class CoGroupByKey<K>

java.lang.Object

org.apache.beam.sdk.transforms.PTransform<KeyedPCollectionTuple<K>,PCollection<KV<K,CoGbkResult>>>

org.apache.beam.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, HasDisplayData

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>() {
       @ProcessElement
       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 org.apache.beam.sdk.transforms.PTransform

name, resourceHints

Method Summary

Modifier and Type	Method and Description
static <K> CoGroupByKey<K>	create() Returns a CoGroupByKey<K> PTransform.
PCollection<KV<K,CoGbkResult>>	expand(KeyedPCollectionTuple<K> input) Override this method to specify how this PTransform should be expanded on the given InputT.

Methods inherited from class org.apache.beam.sdk.transforms.PTransform

compose, compose, getAdditionalInputs, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, getResourceHints, populateDisplayData, setResourceHints, 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

expand

public PCollection<KV<K,CoGbkResult>> expand(KeyedPCollectionTuple<K> input)

Description copied from class: PTransform

Override this method to specify how this PTransform should be expanded on the given InputT.

NOTE: This method should not be called directly. Instead apply the PTransform should be applied to the InputT using the apply method.

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).

Specified by:

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