Package org.apache.beam.sdk.transforms

Class FlatMapElements<InputT,OutputT>

java.lang.Object

org.apache.beam.sdk.transforms.PTransform<PCollection<? extends InputT>,PCollection<OutputT>>

org.apache.beam.sdk.transforms.FlatMapElements<InputT,OutputT>

All Implemented Interfaces:

Serializable, HasDisplayData

public class FlatMapElements<InputT,OutputT>
extends PTransform<PCollection<? extends 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	Description
static class	FlatMapElements.FlatMapWithFailures<InputT,OutputT,FailureT>	A PTransform that adds exception handling to FlatMapElements.

Field Summary

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

annotations, displayData, name, resourceHints

Method Summary

Modifier and Type	Method	Description
<NewFailureT> FlatMapElements.FlatMapWithFailures<InputT,OutputT,NewFailureT>	exceptionsInto(TypeDescriptor<NewFailureT> failureTypeDescriptor)	Returns a new FlatMapElements.FlatMapWithFailures transform that catches exceptions raised while mapping elements, with the given type descriptor used for the failure collection but the exception handler yet to be specified using FlatMapElements.FlatMapWithFailures.exceptionsVia(ProcessFunction).
<FailureT> FlatMapElements.FlatMapWithFailures<InputT,OutputT,FailureT>	exceptionsVia(InferableFunction<WithFailures.ExceptionElement<InputT>,FailureT> exceptionHandler)	Returns a new FlatMapElements.FlatMapWithFailures transform that catches exceptions raised while mapping elements, passing the raised exception instance and the input element being processed through the given exceptionHandler and emitting the result to a failure collection.
PCollection<OutputT>	expand(PCollection<? extends InputT> input)	Override this method to specify how this PTransform should be expanded on the given InputT.
static <OutputT> FlatMapElements<?,OutputT>	into(TypeDescriptor<OutputT> outputType)	Returns a new FlatMapElements transform with the given type descriptor for the output type, but the mapping function yet to be specified using via(ProcessFunction).
void	populateDisplayData(DisplayData.Builder builder)	Register display data for the given transform or component.
<NewInputT> FlatMapElements<NewInputT,OutputT>	via(Contextful<Contextful.Fn<NewInputT,Iterable<OutputT>>> fn)	Like via(ProcessFunction), but allows access to additional context.
static <InputT, OutputT> FlatMapElements<InputT,OutputT>	via(InferableFunction<? super InputT,? extends Iterable<OutputT>> fn)	For a InferableFunction<InputT, ? extends Iterable<OutputT>> fn, return a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.
<NewInputT> FlatMapElements<NewInputT,OutputT>	via(ProcessFunction<NewInputT,? extends Iterable<OutputT>> fn)	For a ProcessFunction<InputT, ? extends Iterable<OutputT>> fn, returns a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.
<NewInputT> FlatMapElements<NewInputT,OutputT>	via(SerializableFunction<NewInputT,? extends Iterable<OutputT>> fn)	Binary compatibility adapter for via(ProcessFunction).
static <InputT, OutputT> FlatMapElements<InputT,OutputT>	via(SimpleFunction<? super InputT,? extends Iterable<OutputT>> fn)	Binary compatibility adapter for via(ProcessFunction).

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

addAnnotation, compose, compose, getAdditionalInputs, getAnnotations, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, getResourceHints, setDisplayData, setResourceHints, toString, validate, validate

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Details

via

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

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

InferableFunction has the advantage of providing type descriptor information, but it is generally more convenient to specify output type via into(TypeDescriptor), and provide the mapping as a lambda expression to via(ProcessFunction).

Example usage:

 PCollection<String> lines = ...;
 PCollection<String> words = lines.apply(FlatMapElements.via(
     new InferableFunction<String, List<String>>() {
       public List<String> apply(String line) throws Exception {
         return Arrays.asList(line.split(" "));
       }
     });
 

via

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

Binary compatibility adapter for via(ProcessFunction).

into

public static <OutputT> FlatMapElements<?,OutputT> into(TypeDescriptor<OutputT> outputType)

Returns a new FlatMapElements transform with the given type descriptor for the output type, but the mapping function yet to be specified using via(ProcessFunction).

via

public <NewInputT>
FlatMapElements<NewInputT,OutputT> via(ProcessFunction<NewInputT,? extends Iterable<OutputT>> fn)

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

Example usage:

 PCollection<String> words = lines.apply(
     FlatMapElements.into(TypeDescriptors.strings())
                    .via((String line) -> Arrays.asList(line.split(" ")))
 

via

public <NewInputT>
FlatMapElements<NewInputT,OutputT> via(SerializableFunction<NewInputT,? extends Iterable<OutputT>> fn)

Binary compatibility adapter for via(ProcessFunction).

via

public <NewInputT>
FlatMapElements<NewInputT,OutputT> via(Contextful<Contextful.Fn<NewInputT,Iterable<OutputT>>> fn)

Like via(ProcessFunction), but allows access to additional context.

expand

public PCollection<OutputT> expand(PCollection<? extends InputT> 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<PCollection<? extends InputT>,PCollection<OutputT>>

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<? extends InputT>,PCollection<OutputT>>

Parameters:

builder - The builder to populate with display data.

See Also:

• HasDisplayData

exceptionsInto

public <NewFailureT>
FlatMapElements.FlatMapWithFailures<InputT,OutputT,NewFailureT> exceptionsInto(TypeDescriptor<NewFailureT> failureTypeDescriptor)

Returns a new FlatMapElements.FlatMapWithFailures transform that catches exceptions raised while mapping elements, with the given type descriptor used for the failure collection but the exception handler yet to be specified using FlatMapElements.FlatMapWithFailures.exceptionsVia(ProcessFunction).

See WithFailures documentation for usage patterns of the returned WithFailures.Result.

exceptionsVia

public <FailureT>
FlatMapElements.FlatMapWithFailures<InputT,OutputT,FailureT> exceptionsVia(InferableFunction<WithFailures.ExceptionElement<InputT>,FailureT> exceptionHandler)

Returns a new FlatMapElements.FlatMapWithFailures transform that catches exceptions raised while mapping elements, passing the raised exception instance and the input element being processed through the given exceptionHandler and emitting the result to a failure collection.

This method takes advantage of the type information provided by InferableFunction, meaning that a call to exceptionsInto(TypeDescriptor) may not be necessary.

See WithFailures documentation for usage patterns of the returned WithFailures.Result.

Example usage:

 Result<PCollection<String>, String>> result = words.apply(
     FlatMapElements
         .into(TypeDescriptors.strings())
         // Could throw ArrayIndexOutOfBoundsException
         .via((String line) -> Arrays.asList(Arrays.copyOfRange(line.split(" "), 1, 5)))
         .exceptionsVia(new WithFailures.ExceptionAsMapHandler<String>() {}));
 PCollection<String> output = result.output();
 PCollection<String> failures = result.failures();