Package org.apache.jackrabbit.oak.segment

Interface Revisions

All Known Implementing Classes:

MemoryStoreRevisions, ReadOnlyRevisions, TarRevisions

public interface Revisions

Revisions instances provide read and write access to the current head state. Implementations are thread safe and all setters act atomically.

This is a low level API and it is the callers and implementors responsibility to ensure all record id passed to or returned from methods of this interface are the ids of node states.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	Revisions.Option	Implementation specific options for the setHead methods.

Method Summary

Modifier and Type	Method	Description
@NotNull RecordId	getHead()	Returns the record id of the head state.
@NotNull RecordId	getPersistedHead()	Returns the persisted to disk record id of the head state.
RecordId	setHead(@NotNull Function<RecordId,RecordId> newHead, @NotNull Revisions.Option... options)	Atomically set the record id of the current head state to the value returned from the newHead function when called with the record id of the current head.
boolean	setHead(@NotNull RecordId expected, @NotNull RecordId head, @NotNull Revisions.Option... options)	Atomically set the record id of the current head state to the given head state if the current head state matches the expected value.

Method Detail

getHead

@NotNull
@NotNull RecordId getHead()

Returns the record id of the head state. The returned id is a valid id for a SegmentNodeState.

Returns:

id of the head state

getPersistedHead

@NotNull
@NotNull RecordId getPersistedHead()

Returns the persisted to disk record id of the head state. The returned id is a valid id for a SegmentNodeState.

Returns:

id of the head state

setHead

boolean setHead(@NotNull
                @NotNull RecordId expected,
                @NotNull
                @NotNull RecordId head,
                @NotNull
                @NotNull Revisions.Option... options)

Atomically set the record id of the current head state to the given head state if the current head state matches the expected value.

All record ids must be valid ids for SegmentNodeStates.

The locking behaviour of this method regarding implementation specific.

Parameters:

expected - the expected head for the update to take place

head - the new head to update to

options - implementation specific options

Returns:

true if the current head was successfully updated, false otherwise.

setHead

RecordId setHead(@NotNull
                 @NotNull Function<RecordId,RecordId> newHead,
                 @NotNull
                 @NotNull Revisions.Option... options)
          throws InterruptedException

Atomically set the record id of the current head state to the value returned from the newHead function when called with the record id of the current head.

All record ids must be valid ids for SegmentNodeStates.

The behaviour of this method regarding locking and handling null values returned by newHead is implementation specific.

Parameters:

newHead - function mapping an record id to the record id to which the current head id should be set.

options - implementation specific options

Returns:

the record id of the root node if the current head was successfully updated, null otherwise.

Throws:

InterruptedException - Blocking implementations may throw this exception whe interrupted.