org.apache.beam.sdk.schemas

Interface ProjectionProducer<T>

@Experimental
public interface ProjectionProducer<T>

A factory for operations that execute a projection on a Schema-aware PCollection.

Typically this interface will be implemented by a reader PTransform or some component thereof that is capable of pushing down a projection to an external source.

Method Summary

Modifier and Type	Method and Description
T	actuateProjectionPushdown(java.lang.String outputId, FieldAccessDescriptor fields) Actuate a projection pushdown.
boolean	supportsProjectionPushdown() Whether this supports projection pushdown.

Method Detail

supportsProjectionPushdown

boolean supportsProjectionPushdown()

Whether this supports projection pushdown.

actuateProjectionPushdown

T actuateProjectionPushdown(java.lang.String outputId,
                            FieldAccessDescriptor fields)

Actuate a projection pushdown.

Parameters:

outputId - The TupleTag id of the target PCollection for the pushdown.

fields - The fields that must be output. Other fields can be dropped.

Returns:

T that implements the projection pushdown. The return value is assumed to be a drop-in replacement for this; it must have all the same functionality. For this reason, T is usually the same class as this.