org.apache.derby.impl.store.raw.xact
Class RowLocking2nohold

java.lang.Object
  extended byorg.apache.derby.impl.store.raw.xact.NoLocking
      extended byorg.apache.derby.impl.store.raw.xact.RowLocking3
          extended byorg.apache.derby.impl.store.raw.xact.RowLockingRR
              extended byorg.apache.derby.impl.store.raw.xact.RowLocking2
                  extended byorg.apache.derby.impl.store.raw.xact.RowLocking2nohold
All Implemented Interfaces:
LockingPolicy

public class RowLocking2nohold
extends RowLocking2

A locking policy that implements row level locking with isolation degree 2, never holding read locks after they are granted. Exactly the same as RowLocking2, except that read locks are acquired using zeroDuration locks, which are immediately released by the lock manager after they are granted.

See Also:
LockingPolicy

Field Summary
 
Fields inherited from class org.apache.derby.impl.store.raw.xact.RowLocking2
 
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
protected RowLocking2nohold(LockFactory lf)
           
 
Method Summary
 boolean lockRecordForRead(Transaction t, ContainerHandle container_handle, RecordHandle record, boolean waitForLock, boolean forUpdate)
          Obtain lock on record being read.
 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.RowLocking2
lockContainer, lockRecordForRead, unlockContainer
 
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, lockRecordForWrite, zeroDurationLockRecordForWrite
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

RowLocking2nohold

protected RowLocking2nohold(LockFactory lf)
Method Detail

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 acquired using zeroDuration lock.

Specified by:
lockRecordForRead in interface LockingPolicy
Overrides:
lockRecordForRead in class RowLocking2
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.
Returns:
true if the lock was granted, false if waitForLock was false and the lock could not be granted.
Throws:
StandardException - Standard exception policy.

unlockRecordAfterRead

public void unlockRecordAfterRead(Transaction t,
                                  ContainerHandle container_handle,
                                  RecordHandle record,
                                  boolean forUpdate,
                                  boolean row_qualified)
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 RowLocking2


Apache Derby V10.0 Engine Documentation - Copyright © 1997,2004 The Apache Software Foundation or its licensors, as applicable.