org.apache.derby.impl.store.raw.xact

Class RowLocking2

java.lang.Object

org.apache.derby.impl.store.raw.xact.NoLocking

org.apache.derby.impl.store.raw.xact.RowLocking3

org.apache.derby.impl.store.raw.xact.RowLockingRR

org.apache.derby.impl.store.raw.xact.RowLocking2

All Implemented Interfaces:

LockingPolicy

Direct Known Subclasses:

RowLocking1, RowLocking2nohold

public class RowLocking2
extends RowLockingRR

A locking policy that implements row level locking with isolation degree 2. The approach is to place all "write" container and row locks on the transaction group lock list. Locks on this group will last until end of transaction. All "read" container and row locks will be placed on a group list, key'd by the ContainerId of the lock. Locks on this list will either be released explicitly by the caller, or will be released as a group when the unlockContainer() call is made. Note that write operations extend from the RowLocking3 implementations.

See Also:

LockingPolicy

Field Summary

Fields

Modifier and Type	Field and Description
private static LockingPolicy	NO_LOCK

Fields inherited from class org.apache.derby.impl.store.raw.xact.RowLocking3

lf

Fields inherited from interface org.apache.derby.iapi.store.raw.LockingPolicy

MODE_CONTAINER, MODE_NONE, MODE_RECORD

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	RowLocking2(LockFactory lf)

Method Summary

Methods

Modifier and Type	Method and Description
boolean	lockContainer(Transaction t, ContainerHandle container, boolean waitForLock, boolean forUpdate) Obtain container level intent lock.
boolean	lockRecordForRead(Transaction t, ContainerHandle container_handle, RecordHandle record, boolean waitForLock, boolean forUpdate) Obtain lock on record being read.
void	unlockContainer(Transaction t, ContainerHandle container_handle) Unlock read locks.
void	unlockRecordAfterRead(Transaction t, ContainerHandle container_handle, RecordHandle record, boolean forUpdate, boolean row_qualified) Unlock a record after it has been locked for read.

Methods inherited from class org.apache.derby.impl.store.raw.xact.RowLockingRR

getReadLockType, getUpdateLockType, getWriteLockType

Methods inherited from class org.apache.derby.impl.store.raw.xact.RowLocking3

getMode, lockRecordForWrite, zeroDurationLockRecordForWrite

Methods inherited from class java.lang.Object

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

Field Detail

NO_LOCK

private static final LockingPolicy NO_LOCK

Constructor Detail

RowLocking2

protected RowLocking2(LockFactory lf)

Method Detail

lockContainer

public boolean lockContainer(Transaction t,
                    ContainerHandle container,
                    boolean waitForLock,
                    boolean forUpdate)
                      throws StandardException

Obtain container level intent lock.

This implementation of row locking is 2 level, ie. table and row locking. It will interact correctly with tables opened with ContainerLocking3 locking mode.

Updater's will get table level IX locks, and X row locks.

Reader's will get table level IS locks, and S row locks.

Read locks are put in a separate "group" from the transaction, so that when the container is closed it can release these read locks.

Specified by:

lockContainer in interface LockingPolicy

Overrides:

lockContainer in class RowLocking3

Parameters:

t - Transaction to associate lock with.

container - Container to lock.

waitForLock - Should lock request wait until granted?

forUpdate - Should container be locked for update, or read?

Returns:

true if the lock was obtained, false if it wasn't. False should only be returned if the waitForLock policy was set to "false," and the lock was unavailable.

Throws:

StandardException - Standard exception policy.

See Also:

ContainerHandle

lockRecordForRead

public boolean lockRecordForRead(Transaction t,
                        ContainerHandle container_handle,
                        RecordHandle record,
                        boolean waitForLock,
                        boolean forUpdate)
                          throws StandardException

Obtain lock on record being read.

Assumes that a table level IS has been acquired. Will acquire a Shared or Update lock on the row, depending on the "forUpdate" parameter.

Read lock will be placed on separate group from transaction.

Specified by:

lockRecordForRead in interface LockingPolicy

Overrides:

lockRecordForRead in class RowLocking3

Parameters:

t - The transaction to associate the lock with.

record - The record to be locked.

waitForLock - Should lock request wait until granted?

forUpdate - Whether to open for read or write access.

container_handle - Open Container used to get record. Will be used to row locks by the container they belong to.

Returns:

true if the lock was granted, false if waitForLock was false and the lock could not be granted.

Throws:

StandardException - Standard exception policy.

See Also:

Page

unlockRecordAfterRead

public void unlockRecordAfterRead(Transaction t,
                         ContainerHandle container_handle,
                         RecordHandle record,
                         boolean forUpdate,
                         boolean row_qualified)
                           throws StandardException

Description copied from class: RowLockingRR

Unlock a record after it has been locked for read.

In repeatable read only unlock records which "did not qualify". For example in a query like "select * from foo where a = 1" on a table with no index it is only necessary to hold locks on rows where a=1, but in the process of finding those rows the system will get locks on other rows to verify they are committed before applying the qualifier. Those locks can be released under repeatable read isolation.

Specified by:

unlockRecordAfterRead in interface LockingPolicy

Overrides:

unlockRecordAfterRead in class RowLockingRR

Throws:

StandardException - Standard exception policy.

See Also:

Page

unlockContainer

public void unlockContainer(Transaction t,
                   ContainerHandle container_handle)

Unlock read locks.

In Cursor stability release all read locks obtained. unlockContainer() will be called when the container is closed.

Specified by:

unlockContainer in interface LockingPolicy

Overrides:

unlockContainer in class NoLocking

Parameters:

t - The transaction to associate the lock with.

container_handle - Container to unlock.

See Also:

ContainerHandle, ContainerHandle.close()