org.apache.hadoop.hbase.regionserver

Class ScannerContext

java.lang.Object

org.apache.hadoop.hbase.regionserver.ScannerContext

Direct Known Subclasses:

NoLimitScannerContext

@InterfaceAudience.LimitedPrivate(value="Coprocesssor")
 @InterfaceStability.Evolving
public class ScannerContext
extends Object

ScannerContext instances encapsulate limit tracking AND progress towards those limits during invocations of InternalScanner.next(java.util.List) and InternalScanner.next(java.util.List).

A ScannerContext instance should be updated periodically throughout execution whenever progress towards a limit has been made. Each limit can be checked via the appropriate checkLimit method.

Once a limit has been reached, the scan will stop. The invoker of InternalScanner.next(java.util.List) or InternalScanner.next(java.util.List) can use the appropriate check*Limit methods to see exactly which limits have been reached. Alternatively, checkAnyLimitReached(LimitScope) is provided to see if ANY limit was reached

NoLimitScannerContext.NO_LIMIT is an immutable static definition that can be used whenever a ScannerContext is needed but limits do not need to be enforced.

NOTE: It is important that this class only ever expose setter methods that can be safely skipped when limits should be NOT enforced. This is because of the necessary immutability of the class NoLimitScannerContext. If a setter cannot be safely skipped, the immutable nature of NoLimitScannerContext will lead to incorrect behavior.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ScannerContext.Builder
static class	ScannerContext.LimitScope The various scopes where a limit can be enforced.
static class	ScannerContext.NextState The possible states a scanner may be in following a call to InternalScanner.next(List)

Method Summary

Modifier and Type	Method and Description
ServerSideScanMetrics	getMetrics() Get the metrics instance.
boolean	isTrackingMetrics()
static ScannerContext.Builder	newBuilder()
static ScannerContext.Builder	newBuilder(boolean keepProgress)
String	toString()

Methods inherited from class java.lang.Object

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

Method Detail

isTrackingMetrics

public boolean isTrackingMetrics()

getMetrics

public ServerSideScanMetrics getMetrics()

Get the metrics instance. Should only be called after a call to isTrackingMetrics() has been made to confirm that metrics are indeed being tracked.

Returns:

ServerSideScanMetrics instance that is tracking metrics for this scan

toString

public String toString()

Overrides:

toString in class Object

newBuilder

public static ScannerContext.Builder newBuilder()

newBuilder

public static ScannerContext.Builder newBuilder(boolean keepProgress)