org.apache.druid.segment

Class ReferenceCountingSegment

java.lang.Object

org.apache.druid.segment.ReferenceCountingCloseableObject<Segment>

org.apache.druid.segment.ReferenceCountingSegment

All Implemented Interfaces:

Closeable, AutoCloseable, ReferenceCountedObject, Segment, SegmentReference, Overshadowable<ReferenceCountingSegment>

public class ReferenceCountingSegment
extends ReferenceCountingCloseableObject<Segment>
implements SegmentReference, Overshadowable<ReferenceCountingSegment>

Segment that is also a ReferenceCountingSegment, allowing query engines that operate directly on segments to track references so that dropping a Segment can be done safely to ensure there are no in-flight queries. Extensions can extend this class for populating VersionedIntervalTimeline with a custom implementation through SegmentLoader.

Field Summary

Fields inherited from class org.apache.druid.segment.ReferenceCountingCloseableObject

baseObject, referents

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ReferenceCountingSegment(Segment baseSegment, int startRootPartitionId, int endRootPartitionId, short minorVersion, short atomicUpdateGroupSize)

Method Summary

Modifier and Type	Method and Description
Optional<Closeable>	acquireReferences() This method is expected to increment a reference count and provide a Closeable that decrements the reference count when closed.
<T> T	as(Class<T> clazz) Request an implementation of a particular interface.
QueryableIndex	asQueryableIndex()
StorageAdapter	asStorageAdapter()
short	getAtomicUpdateGroupSize() Return the size of atomicUpdateGroup.
Segment	getBaseSegment()
org.joda.time.Interval	getDataInterval()
int	getEndRootPartitionId() See doc of Overshadowable.getStartRootPartitionId().
SegmentId	getId()
short	getMinorVersion()
int	getStartRootPartitionId() All overshadowables have root partition range.
String	getVersion()
boolean	overshadows(ReferenceCountingSegment other) Returns true if this overshadowable overshadows the other.
static ReferenceCountingSegment	wrapRootGenerationSegment(Segment baseSegment)
static ReferenceCountingSegment	wrapSegment(Segment baseSegment, ShardSpec shardSpec)

Methods inherited from class org.apache.druid.segment.ReferenceCountingCloseableObject

close, decrement, decrementOnceCloseable, getNumReferences, increment, incrementReferenceAndDecrementOnceCloseable, isClosed

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.io.Closeable

close

Methods inherited from interface org.apache.druid.timeline.Overshadowable

containsRootPartition, hasData

Constructor Detail

ReferenceCountingSegment

protected ReferenceCountingSegment(Segment baseSegment,
                                   int startRootPartitionId,
                                   int endRootPartitionId,
                                   short minorVersion,
                                   short atomicUpdateGroupSize)

Method Detail

wrapRootGenerationSegment

public static ReferenceCountingSegment wrapRootGenerationSegment(Segment baseSegment)

wrapSegment

public static ReferenceCountingSegment wrapSegment(Segment baseSegment,
                                                   ShardSpec shardSpec)

getBaseSegment

@Nullable
public Segment getBaseSegment()

getId

@Nullable
public SegmentId getId()

Specified by:

getId in interface Segment

getDataInterval

@Nullable
public org.joda.time.Interval getDataInterval()

Specified by:

getDataInterval in interface Segment

asQueryableIndex

@Nullable
public QueryableIndex asQueryableIndex()

Specified by:

asQueryableIndex in interface Segment

asStorageAdapter

@Nullable
public StorageAdapter asStorageAdapter()

Specified by:

asStorageAdapter in interface Segment

overshadows

public boolean overshadows(ReferenceCountingSegment other)

Description copied from interface: Overshadowable

Returns true if this overshadowable overshadows the other.

Specified by:

overshadows in interface Overshadowable<ReferenceCountingSegment>

getStartRootPartitionId

public int getStartRootPartitionId()

Description copied from interface: Overshadowable

All overshadowables have root partition range. First-generation overshadowables have (partitionId, partitionId + 1) as their root partition range. Non-first-generation overshadowables are the overshadowables that overwrite first or non-first generation overshadowables, and they have the merged root partition range of all overwritten first-generation overshadowables. Note that first-generation overshadowables can be overwritten by a single non-first-generation overshadowable if they have consecutive partitionId. Non-first-generation overshadowables can be overwritten by another if their root partition ranges are consecutive.

Specified by:

getStartRootPartitionId in interface Overshadowable<ReferenceCountingSegment>

getEndRootPartitionId

public int getEndRootPartitionId()

Description copied from interface: Overshadowable

See doc of Overshadowable.getStartRootPartitionId().

Specified by:

getEndRootPartitionId in interface Overshadowable<ReferenceCountingSegment>

getVersion

public String getVersion()

Specified by:

getVersion in interface Overshadowable<ReferenceCountingSegment>

getMinorVersion

public short getMinorVersion()

Specified by:

getMinorVersion in interface Overshadowable<ReferenceCountingSegment>

getAtomicUpdateGroupSize

public short getAtomicUpdateGroupSize()

Description copied from interface: Overshadowable

Return the size of atomicUpdateGroup. An atomicUpdateGroup is a set of segments which should be updated all together atomically in VersionedIntervalTimeline.

Specified by:

getAtomicUpdateGroupSize in interface Overshadowable<ReferenceCountingSegment>

acquireReferences

public Optional<Closeable> acquireReferences()

Description copied from interface: ReferenceCountedObject

This method is expected to increment a reference count and provide a Closeable that decrements the reference count when closed. This is likely just a wrapper around ReferenceCountingCloseableObject.incrementReferenceAndDecrementOnceCloseable(), but may also include any other associated references which should be incremented when this method is called, and decremented/released by the closeable. IMPORTANT NOTE: to fulfill the contract of this method, implementors must return a closeable to indicate that the reference can be acquired, even if there is nothing to close. Implementors should avoid allowing this method or the Closeable it creates to throw exceptions. For callers: if this method returns non-empty, IT MUST BE CLOSED, else reference counts can potentially leak.

Specified by:

acquireReferences in interface ReferenceCountedObject

as

public <T> T as(Class<T> clazz)

Description copied from interface: Segment

Request an implementation of a particular interface. If the passed-in interface is QueryableIndex or StorageAdapter, then this method behaves identically to Segment.asQueryableIndex() or Segment.asStorageAdapter(). Other interfaces are only expected to be requested by callers that have specific knowledge of extra features provided by specific segment types. For example, an extension might provide a custom Segment type that can offer both StorageAdapter and some new interface. That extension can also offer a Query that uses that new interface. Implementations which accept classes other than QueryableIndex or StorageAdapter are limited to using those classes within the extension. This means that one extension cannot rely on the `Segment.as` behavior of another extension.

Specified by:

as in interface Segment

Type Parameters:

T - desired interface

Parameters:

clazz - desired interface

Returns:

instance of clazz, or null if the interface is not supported by this segment