Package org.apache.drill.exec.physical.impl.protocol

Class OperatorDriver

java.lang.Object

org.apache.drill.exec.physical.impl.protocol.OperatorDriver

public class OperatorDriver
extends Object

State machine that drives the operator executable. Converts between the iterator protocol and the operator executable protocol. Implemented as a separate class in anticipation of eventually changing the record batch (iterator) protocol.

Schema-Only Batch

The scan operator is designed to provide an initial, empty, schema-only batch. At the time that this code was written, it was (mis-?) understood that Drill used a "fast schema" path that provided a schema-only batch as the first batch. However, it turns out that most operators fail when presented with an empty batch: many do not properly set the offset vector for variable-width vectors to an initial 0 position, causing all kinds of issues.

To work around this issue, the code defaults to *not* providing the schema batch.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	OperatorDriver.State

Constructor Summary

Constructors

Constructor	Description
OperatorDriver(OperatorContext opContext, OperatorExec opExec, boolean enableSchemaBatch)

Method Summary

Modifier and Type	Method	Description
BatchAccessor	batchAccessor()
void	cancel()	Cancels the operator before reaching EOF.
void	close()
RecordBatch.IterOutcome	next()	Get the next batch.
OperatorContext	operatorContext()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

OperatorDriver

public OperatorDriver(OperatorContext opContext,
 OperatorExec opExec,
 boolean enableSchemaBatch)

Method Details

next

public RecordBatch.IterOutcome next()

Get the next batch. Performs initialization on the first call.

Returns:

the iteration outcome to send downstream

cancel

public void cancel()

Cancels the operator before reaching EOF.

close

public void close()

batchAccessor

public BatchAccessor batchAccessor()

operatorContext

public OperatorContext operatorContext()