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 created by calling Pipeline.begin() on a Pipeline.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
<OutputT extends POutput> OutputT	apply(PTransform<? super PBegin,OutputT> t) Like apply(String, PTransform) but defaulting to the name of the PTransform.
<OutputT extends POutput> OutputT	apply(String name, PTransform<? super PBegin,OutputT> t) Applies the given PTransform to this input PBegin, using name to identify this specific application of the transform.
Collection<? extends PValue>	expand() Expands this PInput into a list of its component output PValues.
void	finishSpecifying() After building, finalizes this PInput to make it ready for being used as an input to a PTransform.
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 Detail

PBegin

protected PBegin(Pipeline pipeline)

Constructs a PBegin in the given Pipeline.

Method Detail

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 input 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 Collection<? extends 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

finishSpecifying

public void finishSpecifying()

Description copied from interface: PInput

After building, finalizes this PInput to make it ready for being used as an input to a PTransform.

Automatically invoked whenever apply() is invoked on this PInput, so users do not normally call this explicitly.

Specified by:

finishSpecifying in interface PInput