Package com.twilio.kudu.sql

Class CalciteScannerMessage<T>

java.lang.Object

com.twilio.kudu.sql.CalciteScannerMessage<T>

Type Parameters:

T - The Calcite type. For multicolumn rows it is an Object[] for single it is Object

public final class CalciteScannerMessage<T>
extends Object

Message object represents a Message from an active scanner. There are multiple types defined in CalciteScannerMessage.MessageType and each consumer is expected handle each type. Types are 1. ROW -- contains a row 2. CLOSE -- scanner is closing so shouldn't expect any more ROW 3. ERROR -- scanner failed in some manner, contains a failure. When an ERROR message is received, the producer needs to produce a CLOSE message just after. ERROR message is not terminal, only CLOSE is terminal We use this in a Queue as the only synchronization and shared state between a ScannerCallback and CalciteKuduEnumerable. A Queue with heterogeneous messages is the only solution we were able to make work. Using a queue and another synchronization object did not work.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	CalciteScannerMessage.MessageType

Field Summary

Fields

Modifier and Type	Field	Description
final Optional<ScannerCallback>	callback
final Optional<Exception>	failure
final Optional<T>	row
final CalciteScannerMessage.MessageType	type

Constructor Summary

Constructors

Constructor	Description
CalciteScannerMessage(ScannerCallback callback)	Constructs a Batch Completed Scanner Message.
CalciteScannerMessage(Exception failure)	Construct a Scanner Message that contains an exception.
CalciteScannerMessage(T row)	Constructs a Scanner Message that contains a row.

Method Summary

Modifier and Type	Method	Description
static <T> CalciteScannerMessage<T>	createEndMessage()	Construct a CalciteScannerMessage.MessageType.CLOSE message to represent closing of the scanner.
boolean	isTerminal()	Whether or not this message means the end of the scan

Methods inherited from class java.lang.Object

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

Field Details

type

public final CalciteScannerMessage.MessageType type

row

public final Optional<T> row

failure

public final Optional<Exception> failure

callback

public final Optional<ScannerCallback> callback

Constructor Details

CalciteScannerMessage

public CalciteScannerMessage(Exception failure)

Construct a Scanner Message that contains an exception. When this message is consumed the consumer is _expected_ to throw the exception.

Parameters:

failure - the exception this message represents

CalciteScannerMessage

public CalciteScannerMessage(T row)

Constructs a Scanner Message that contains a row. Row must by nonNull

Parameters:

row - the T that should be consumed.

CalciteScannerMessage

public CalciteScannerMessage(ScannerCallback callback)

Constructs a Batch Completed Scanner Message.

Parameters:

callback - the ScannerCallback that completed it's batch

Method Details

createEndMessage

public static <T> CalciteScannerMessage<T> createEndMessage()

Construct a CalciteScannerMessage.MessageType.CLOSE message to represent closing of the scanner. The consumer is excepted to keep track of closed scanners and should not expect more CalciteScannerMessage.MessageType.ROW from the scanner.

Type Parameters:

T - The Calcite type. For multicolumn rows it is an Object[] for single it is Object

Returns:

simple CalciteScannerMessage.MessageType.CLOSE message.

isTerminal

public boolean isTerminal()

Whether or not this message means the end of the scan

Returns:

true if the scanner is no longer processing rows.