ProjectionProducer (core 2.44.0 API)

```
@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

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	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.