org.apache.drill.exec.physical.impl

Interface OutputMutator

All Known Implementing Classes:

ScanBatch.Mutator

public interface OutputMutator

Interface that allows a record reader to modify the current schema. The output mutator interface abstracts ValueVector creation and maintenance away from any particular RecordReader. This means, among other things, that a new RecordReader that shares the same column definitions in a different order does not generate a Schema change event for downstream consumers.

Method Summary

Modifier and Type	Method and Description
<T extends ValueVector> T	addField(MaterializedField field, Class<T> clazz) Add a ValueVector for new (or existing) field.
void	allocate(int recordCount)
void	clear() Clear this mutator i.e.
CallBack	getCallBack()
DrillBuf	getManagedBuffer() Allows a scanner to request a set of managed block of memory.
boolean	isNewSchema() Whether or not the fields added to the OutputMutator generated a new schema event.

Method Detail

addField

<T extends ValueVector> T addField(MaterializedField field,
                                   Class<T> clazz)
                            throws SchemaChangeException

Add a ValueVector for new (or existing) field.

Parameters:

field - The specification of the newly desired vector.

clazz - The expected ValueVector class. Also allows strongly typed use of this interface.

Returns:

The existing or new ValueVector associated with the provided field.

Throws:

SchemaChangeException - If the addition of this field is incompatible with this OutputMutator's capabilities.

allocate

void allocate(int recordCount)

isNewSchema

boolean isNewSchema()

Whether or not the fields added to the OutputMutator generated a new schema event.

Returns:

getManagedBuffer

DrillBuf getManagedBuffer()

Allows a scanner to request a set of managed block of memory.

Returns:

A DrillBuf that will be released at the end of the current query (and can be resized as desired during use).

getCallBack

CallBack getCallBack()

Returns:

the CallBack object for this mutator

clear

void clear()

Clear this mutator i.e. reset it to pristine condition