com.google.cloud.dataflow.sdk.transforms

Class FlatMapElements<InputT,OutputT>

java.lang.Object

com.google.cloud.dataflow.sdk.transforms.PTransform<PCollection<InputT>,PCollection<OutputT>>

com.google.cloud.dataflow.sdk.transforms.FlatMapElements<InputT,OutputT>

All Implemented Interfaces:

Serializable

public class FlatMapElements<InputT,OutputT>
extends PTransform<PCollection<InputT>,PCollection<OutputT>>

PTransforms for mapping a simple function that returns iterables over the elements of a PCollection and merging the results.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FlatMapElements.MissingOutputTypeDescriptor<InputT,OutputT> An intermediate builder for a FlatMapElements transform.

Field Summary

Fields inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform

name

Method Summary

Modifier and Type	Method and Description
PCollection<OutputT>	apply(PCollection<InputT> input) Applies this PTransform on the given InputT, and returns its Output.
static <InputT,OutputT> FlatMapElements.MissingOutputTypeDescriptor<InputT,OutputT>	via(SerializableFunction<InputT,? extends Iterable<OutputT>> fn) For a SerializableFunction<InputT, ? extends Iterable<OutputT>> fn, returns a PTransform that applies {@code fn} to every element of the input {@code PCollection} and outputs all of the elements to the output {@code PCollection}.
static <InputT,OutputT> FlatMapElements<InputT,OutputT>	via(SimpleFunction<InputT,? extends Iterable<OutputT>> fn) For a SimpleFunction<InputT, ? extends Iterable<OutputT>> fn, return a PTransform that applies {@code fn} to every element of the input {@code PCollection} and outputs all of the elements to the output {@code PCollection}.

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

via

public static <InputT,OutputT> FlatMapElements.MissingOutputTypeDescriptor<InputT,OutputT> via(SerializableFunction<InputT,? extends Iterable<OutputT>> fn)

For a SerializableFunction<InputT, ? extends Iterable<OutputT>> fn, returns a PTransform that applies {@code fn} to every element of the input {@code PCollection} and outputs all of the elements to the output {@code PCollection}.

Example of use in Java 8:

{@code
 PCollection words = lines.apply(
     FlatMapElements.via((String line) -> Arrays.asList(line.split(" ")))
         .withOutputType(new TypeDescriptor(){});
 }

In Java 7, the overload {@link #via(SimpleFunction)} is more concise as the output type descriptor need not be provided.

via

public static <InputT,OutputT> FlatMapElements<InputT,OutputT> via(SimpleFunction<InputT,? extends Iterable<OutputT>> fn)

For a SimpleFunction<InputT, ? extends Iterable<OutputT>> fn, return a PTransform that applies {@code fn} to every element of the input {@code PCollection} and outputs all of the elements to the output {@code PCollection}.

This overload is intended primarily for use in Java 7. In Java 8, the overload {@link #via(SerializableFunction)} supports use of lambda for greater concision.

Example of use in Java 7:

{@code
 PCollection lines = ...;
 PCollection words = lines.apply(FlatMapElements.via(
     new SimpleFunction>() {
       public Integer apply(String line) {
         return Arrays.asList(line.split(" "));
       }
     });
 }

To use a Java 8 lambda, see {@link #of(SerializableFunction, TypeDescriptor)}.

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>>