org.apache.derby.impl.store.raw.xact
Class RowLocking1
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
org.apache.derby.impl.store.raw.xact.RowLocking1
- All Implemented Interfaces:
- LockingPolicy
- public class RowLocking1
- extends RowLocking2
A locking policy that implements row level locking with isolation degree 1.
This is an implementation of Gray's degree 1 isolation, read uncommitted,
or often referred to as dirty reads. Basically read operations are
done with no locking.
This locking policy is only to be used for read operations.
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.
This implementation will still get table level intent locks. This is to
prevent hard cases where the container otherwise could be deleted while
read uncommitted reader is still accessing it. In order to not get table
level intent locks some sort of other ddl level lock would have to be
implemented.
All "read" row locks will be not be requested.
Note that write operations extend from the RowLocking3 implementations.
- See Also:
LockingPolicy
Fields inherited from class org.apache.derby.impl.store.raw.xact.RowLocking2 |
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Fields inherited from class org.apache.derby.impl.store.raw.xact.RowLocking3 |
lf |
Method Summary |
void |
lockRecordForRead(Latch latch,
RecordHandle record,
boolean forUpdate)
Obtain lock on record being read while holding a latch.
|
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.
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Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
RowLocking1
protected RowLocking1(LockFactory lf)
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 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.
lockRecordForRead
public void lockRecordForRead(Latch latch,
RecordHandle record,
boolean forUpdate)
throws StandardException
- Obtain lock on record being read while holding a latch.
Assumes that a table level IS has been acquired. Will acquire a Shared
or Update lock on the row, depending on the "forUpdate" parameter.
- Specified by:
lockRecordForRead
in interface LockingPolicy
- Overrides:
lockRecordForRead
in class RowLocking2
- Parameters:
latch
- The latch being held.record
- The record to be locked.forUpdate
- Whether to open for read or write access.
- Throws:
StandardException
- Standard exception policy.
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 RowLocking2
- Throws:
StandardException
Apache Derby V10.1 Engine Documentation - Copyright © 1997,2005 The Apache Software Foundation or its licensors, as applicable.