org.apache.drill.exec.physical.impl.scan.v3.lifecycle

Class BaseTestScanLifecycle.MockThreeColReader

java.lang.Object

org.apache.drill.exec.physical.impl.scan.v3.lifecycle.BaseTestScanLifecycle.MockThreeColReader

All Implemented Interfaces:

ManagedReader

Enclosing class:

BaseTestScanLifecycle

protected static class BaseTestScanLifecycle.MockThreeColReader
extends Object
implements ManagedReader

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.drill.exec.physical.impl.scan.v3.ManagedReader

ManagedReader.EarlyEofException

Field Summary

Fields

Modifier and Type	Field and Description
static TupleMetadata	READER_SCHEMA

Constructor Summary

Constructors

Constructor and Description
MockThreeColReader(SchemaNegotiator negotiator)

Method Summary

Modifier and Type	Method and Description
void	close() Release resources.
boolean	next() Read the next batch.

Methods inherited from class java.lang.Object

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

Field Detail

READER_SCHEMA

public static final TupleMetadata READER_SCHEMA

Constructor Detail

MockThreeColReader

public MockThreeColReader(SchemaNegotiator negotiator)

Method Detail

next

public boolean next()

Description copied from interface: ManagedReader

Read the next batch. Reading continues until either EOF, or until the mutator indicates that the batch is full. The batch is considered valid if it is non-empty. Returning true with an empty batch is valid, and is helpful on the very first batch (returning schema only.) An empty batch with a false return code indicates EOF and the batch will be discarded. A non-empty batch along with a false return result indicates a final, valid batch, but that EOF was reached and no more data is available.

This somewhat complex protocol avoids the need to allocate a final batch just to find out that no more data is available; it allows EOF to be returned along with the final batch.

Specified by:

next in interface ManagedReader

Returns:

true if more data may be available (and so next() should be called again, false to indicate that EOF was reached

close

public void close()

Description copied from interface: ManagedReader

Release resources. Called just after a failure, when the scanner is cancelled, or after next() returns EOF. Release all resources and close files. Guaranteed to be called if open() returns normally; will not be called if open() throws an exception.

Specified by:

close in interface ManagedReader