Package org.h2.mvstore

Class RootReference<K,V>

java.lang.Object

org.h2.mvstore.RootReference<K,V>

public final class RootReference<K,V>
extends java.lang.Object

Class RootReference is an immutable structure to represent state of the MVMap as a whole (not related to a particular B-Tree node). Single structure would allow for non-blocking atomic state change. The most important part of it is a reference to the root node.

Field Summary

Fields

Modifier and Type	Field	Description
private byte	appendCounter	Size of the occupied part of the append buffer.
private byte	holdCount	Counter of reentrant locks.
private long	ownerId	Lock owner thread id.
(package private) RootReference<K,V>	previous	Reference to the previous root in the chain.
Page<K,V>	root	The root page.
(package private) long	updateAttemptCounter	Counter for attempted root updates.
(package private) long	updateCounter	Counter for successful root updates.
long	version	The version used for writing.

Constructor Summary

Constructors

Modifier	Constructor	Description
(package private)	RootReference(Page<K,V> root, long version)
private	RootReference(RootReference<K,V> r, int attempt)
private	RootReference(RootReference<K,V> r, long version, int attempt)
private	RootReference(RootReference<K,V> r, Page<K,V> root, boolean keepLocked, int appendCounter)
private	RootReference(RootReference<K,V> r, Page<K,V> root, long updateAttemptCounter)

Method Summary

Modifier and Type	Method	Description
private boolean	canUpdate()
(package private) int	getAppendCounter()
long	getTotalCount()
(package private) long	getVersion()
(package private) boolean	hasChangesSince(long version, boolean persistent)	Does the root have changes since the specified version?
private boolean	isFree()
(package private) boolean	isLocked()
boolean	isLockedByCurrentThread()
boolean	needFlush()	Whether flushing is needed.
(package private) void	removeUnusedOldVersions(long oldestVersionToKeep)	Removed old versions that are not longer used.
java.lang.String	toString()
(package private) RootReference<K,V>	tryLock(int attemptCounter)	Try to lock.
(package private) RootReference<K,V>	tryUnlockAndUpdateVersion(long version, int attempt)	Try to unlock, and if successful update the version
private RootReference<K,V>	tryUpdate(RootReference<K,V> updatedRootReference)
(package private) RootReference<K,V>	updatePageAndLockedStatus(Page<K,V> page, boolean keepLocked, int appendCounter)	Update the page, possibly keeping it locked.
(package private) RootReference<K,V>	updateRootPage(Page<K,V> newRootPage, long attemptCounter)	Try to unlock.

Methods inherited from class java.lang.Object

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

Field Detail

root

public final Page<K,V> root

The root page.

version

public final long version

The version used for writing.

holdCount

private final byte holdCount

Counter of reentrant locks.

ownerId

private final long ownerId

Lock owner thread id.

previous

volatile RootReference<K,V> previous

Reference to the previous root in the chain. That is the last root of the previous version, which had any data changes. Versions without any data changes are dropped from the chain, as it built.

updateCounter

final long updateCounter

Counter for successful root updates.

updateAttemptCounter

final long updateAttemptCounter

Counter for attempted root updates.

appendCounter

private final byte appendCounter

Size of the occupied part of the append buffer.

Constructor Detail

RootReference

RootReference(Page<K,V> root,
              long version)

RootReference

private RootReference(RootReference<K,V> r,
                      Page<K,V> root,
                      long updateAttemptCounter)

RootReference

private RootReference(RootReference<K,V> r,
                      int attempt)

RootReference

private RootReference(RootReference<K,V> r,
                      Page<K,V> root,
                      boolean keepLocked,
                      int appendCounter)

RootReference

private RootReference(RootReference<K,V> r,
                      long version,
                      int attempt)

Method Detail

updateRootPage

RootReference<K,V> updateRootPage(Page<K,V> newRootPage,
                                        long attemptCounter)

Try to unlock.

Parameters:

newRootPage - the new root page

attemptCounter - the number of attempts so far

Returns:

the new, unlocked, root reference, or null if not successful

tryLock

RootReference<K,V> tryLock(int attemptCounter)

Try to lock.

Parameters:

attemptCounter - the number of attempts so far

Returns:

the new, locked, root reference, or null if not successful

tryUnlockAndUpdateVersion

RootReference<K,V> tryUnlockAndUpdateVersion(long version,
                                                   int attempt)

Try to unlock, and if successful update the version

Parameters:

version - the version

attempt - the number of attempts so far

Returns:

the new, unlocked and updated, root reference, or null if not successful

updatePageAndLockedStatus

RootReference<K,V> updatePageAndLockedStatus(Page<K,V> page,
                                                   boolean keepLocked,
                                                   int appendCounter)

Update the page, possibly keeping it locked.

Parameters:

page - the page

keepLocked - whether to keep it locked

appendCounter - number of items in append buffer

Returns:

the new root reference, or null if not successful

removeUnusedOldVersions

void removeUnusedOldVersions(long oldestVersionToKeep)

Removed old versions that are not longer used.

Parameters:

oldestVersionToKeep - the oldest version that needs to be retained

isLocked

boolean isLocked()

isFree

private boolean isFree()

canUpdate

private boolean canUpdate()

isLockedByCurrentThread

public boolean isLockedByCurrentThread()

tryUpdate

private RootReference<K,V> tryUpdate(RootReference<K,V> updatedRootReference)

getVersion

long getVersion()

hasChangesSince

boolean hasChangesSince(long version,
                        boolean persistent)

Does the root have changes since the specified version?

Parameters:

version - to check against

persistent - whether map is backed by persistent storage

Returns:

true if this root has unsaved changes

getAppendCounter

int getAppendCounter()

needFlush

public boolean needFlush()

Whether flushing is needed.

Returns:

true if yes

getTotalCount

public long getTotalCount()

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object