org.apache.beam.sdk.schemas

Interface ProjectionProducer<T>

All Known Implementing Classes:

BigQueryIO.TypedRead

@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.util.Map<TupleTag<?>,FieldAccessDescriptor> outputFields) 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.util.Map<TupleTag<?>,FieldAccessDescriptor> outputFields)

Actuate a projection pushdown.

Parameters:

outputFields - Map keyed by the TupleTag for each output on which pushdown is requested. The value is the FieldAccessDescriptor containing the list of fields needed for that output; fields not present in the descriptor should 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.