Package org.apache.beam.sdk.values

Class PBegin

java.lang.Object

org.apache.beam.sdk.values.PBegin

All Implemented Interfaces:

PInput

public class PBegin
extends Object
implements PInput

PBegin is the "input" to a root PTransform, such as Read or Create.

Typically elided by simply calling Pipeline.apply(String, PTransform) or Pipeline.apply(PTransform), but one can be explicitly created by calling Pipeline.begin() on a Pipeline.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	PBegin(Pipeline pipeline)	Constructs a PBegin in the given Pipeline.

Method Summary

Modifier and Type	Method	Description
<OutputT extends POutput> OutputT	apply(String name, PTransform<? super PBegin,OutputT> t)	Applies the given PTransform to this PBegin, using name to identify this specific application of the transform.
<OutputT extends POutput> OutputT	apply(PTransform<? super PBegin,OutputT> t)	Like apply(String, PTransform) but defaulting to the name of the PTransform.
Map<TupleTag<?>,PValue>	expand()	Expands this PInput into a list of its component output PValues.
Pipeline	getPipeline()	Returns the owning Pipeline of this PInput.
static PBegin	in(Pipeline pipeline)	Returns a PBegin in the given Pipeline.

Methods inherited from class java.lang.Object

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

Constructor Details

PBegin

protected PBegin(Pipeline pipeline)

Constructs a PBegin in the given Pipeline.

Method Details

in

public static PBegin in(Pipeline pipeline)

Returns a PBegin in the given Pipeline.

apply

public <OutputT extends POutput> OutputT apply(PTransform<? super PBegin,OutputT> t)

Like apply(String, PTransform) but defaulting to the name of the PTransform.

apply

public <OutputT extends POutput> OutputT apply(String name,
 PTransform<? super PBegin,OutputT> t)

Applies the given PTransform to this PBegin, using name to identify this specific application of the transform.

This name is used in various places, including the monitoring UI, logging, and to stably identify this application node in the job graph.

getPipeline

public Pipeline getPipeline()

Description copied from interface: PInput

Returns the owning Pipeline of this PInput.

Specified by:

getPipeline in interface PInput

expand

public Map<TupleTag<?>,PValue> expand()

Description copied from interface: PInput

Expands this PInput into a list of its component output PValues.

• A PValue expands to itself.
• A tuple or list of PValues (such as PCollectionTuple or PCollectionList) expands to its component PValue PValues.

Not intended to be invoked directly by user code.

Specified by:

expand in interface PInput