Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.impl.services.locks.LockSpace

A LockSpace represents the complete set of locks held within a single compatibility space, broken into groups of locks. A LockSpace contains a HashMap keyed by the group reference, the data for each key is a HashMap of Lock's.

A LockSpace can have an owner (for instance a transaction). Currently, the owner is used by the virtual lock table to find out which transaction a lock belongs to. Some parts of the code also use the owner as a group object which guarantees that the lock is released on a commit or an abort. The owner has no special meaning to the lock manager and can be any object, including null.

Field Summary

Modifier and Type	Field and Description
private Limit	callback
private Object	callbackGroup
private final HashMap<Object, HashMap<Lock, Lock>>	groups Map from group references to groups of locks.
private boolean	inLimit
private int	limit
private static final int	MAX_CACHED_GROUPS The maximum number of elements to cache in `spareGroups`.
private int	nextLimitCall
private final LockOwner	owner Reference to the owner of this compatibility space.
private final ArrayDeque<HashMap<Lock, Lock>>	spareGroups Cached HashMaps for storing lock groups.

Constructor Summary

Access	Constructor and Description
pack-priv	LockSpace(LockOwner an object representing the owner of the compatibility space owner) Creates a new `LockSpace` instance.

Method Summary

Modifier and Type	Method and Description
protected synchronized void	addLock(Object group, Lock lock) Add a lock to a group.
pack-priv synchronized boolean	areLocksHeld(Object group) Return true if locks are held in a group
pack-priv synchronized boolean	Returns: true if locks are held, false otherwise areLocksHeld() Return true if locks are held in this compatibility space.
pack-priv synchronized void	clearLimit(Object group) Clear a limit set by setLimit.
pack-priv synchronized int	deadlockCount(int bail) Return a count of the number of locks held by this space.
private HashMap<Lock, Lock>	getGroupMap(Object group)
public LockOwner	Returns: the owner of the compatibility space getOwner() Implements org.apache.derby.iapi.services.locks.CompatibilitySpace.getOwner. Get the object representing the owner of the compatibility space.
pack-priv synchronized boolean	isLockHeld(Object group, Lockable ref, Object qualifier)
private void	mergeGroups(HashMap<Lock, Lock> from, HashMap<Lock, Lock> into)
private void	saveGroup(HashMap<Lock, Lock> dl)
pack-priv synchronized void	setLimit(Object group, int limit, Limit callback)
pack-priv synchronized void	transfer(Object oldGroup, Object newGroup)
pack-priv synchronized void	unlockGroup(LockTable lset, Object group) Unlock all the locks in a group and then remove the group.
pack-priv synchronized void	unlockGroup(LockTable lset, Object group, Matchable key) Unlock all locks in the group that match the key
pack-priv synchronized int	unlockReference(LockTable lset, Lockable ref, Object qualifier, Object group)

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

callback	back to summary
private Limit callback

callbackGroup	back to summary
private Object callbackGroup

groups	back to summary
private final HashMap<Object, HashMap<Lock, Lock>> groups Map from group references to groups of locks.

inLimit	back to summary
private boolean inLimit

limit	back to summary
private int limit

MAX_CACHED_GROUPS	back to summary
private static final int MAX_CACHED_GROUPS The maximum number of elements to cache in `spareGroups`.

nextLimitCall	back to summary
private int nextLimitCall

owner	back to summary
private final LockOwner owner Reference to the owner of this compatibility space.

spareGroups	back to summary
private final ArrayDeque<HashMap<Lock, Lock>> spareGroups Cached HashMaps for storing lock groups.

Constructor Detail

LockSpace back to summary

LockSpace	back to summary
pack-priv LockSpace(LockOwner owner) Creates a new `LockSpace` instance. Parameters owner:LockOwner an object representing the owner of the compatibility space

pack-priv LockSpace(LockOwner owner)

Creates a new LockSpace instance.

Parameters

owner:LockOwner: an object representing the owner of the compatibility space

Method Detail

addLock	back to summary
protected synchronized void addLock(Object group, Lock lock) throws StandardException Add a lock to a group.

areLocksHeld	back to summary
pack-priv synchronized boolean areLocksHeld(Object group) Return true if locks are held in a group

areLocksHeld	back to summary
pack-priv synchronized boolean areLocksHeld() Return true if locks are held in this compatibility space. Returns:boolean true if locks are held, false otherwise

areLocksHeld

back to summary

pack-priv synchronized boolean areLocksHeld()

Return true if locks are held in this compatibility space.

Returns:boolean: true if locks are held, false otherwise

clearLimit	back to summary
pack-priv synchronized void clearLimit(Object group) Clear a limit set by setLimit.

deadlockCount	back to summary
pack-priv synchronized int deadlockCount(int bail) Return a count of the number of locks held by this space. The argument bail indicates at which point the counting should bail out and return the current count. This routine will bail if the count is greater than bail. Thus this routine is intended to for deadlock code to find the space with the fewest number of locks.

getGroupMap	back to summary
private HashMap<Lock, Lock> getGroupMap(Object group)

getOwner	back to summary
public LockOwner getOwner() Implements org.apache.derby.iapi.services.locks.CompatibilitySpace.getOwner. Get the object representing the owner of the compatibility space. Returns:LockOwner the owner of the compatibility space

getOwner

back to summary

public LockOwner getOwner()

Implements org.apache.derby.iapi.services.locks.CompatibilitySpace.getOwner.

Get the object representing the owner of the compatibility space.

Returns:LockOwner: the owner of the compatibility space

isLockHeld	back to summary
pack-priv synchronized boolean isLockHeld(Object group, Lockable ref, Object qualifier)

mergeGroups	back to summary
private void mergeGroups(HashMap<Lock, Lock> from, HashMap<Lock, Lock> into)

saveGroup	back to summary
private void saveGroup(HashMap<Lock, Lock> dl)

setLimit	back to summary
pack-priv synchronized void setLimit(Object group, int limit, Limit callback)

transfer	back to summary
pack-priv synchronized void transfer(Object oldGroup, Object newGroup)

unlockGroup	back to summary
pack-priv synchronized void unlockGroup(LockTable lset, Object group) Unlock all the locks in a group and then remove the group.

unlockGroup	back to summary
pack-priv synchronized void unlockGroup(LockTable lset, Object group, Matchable key) Unlock all locks in the group that match the key