Top Description Constructors Methods
org.apache.derby.impl.store.raw.xact

public Class RowLocking1

extends RowLocking2
Class Inheritance
Imports
org.apache.derby.iapi.services.locks.LockFactory, org.apache.derby.shared.common.sanity.SanityManager, org.apache.derby.iapi.store.raw.ContainerHandle, .ContainerLock, .LockingPolicy, .RecordHandle, .RowLock, .Transaction, org.apache.derby.shared.common.error.StandardException
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
org.apache.derby.iapi.store.raw.LockingPolicy

Constructor Summary

AccessConstructor and Description
protected
RowLocking1(LockFactory lf)

Method Summary

Modifier and TypeMethod and Description
public boolean

Returns:

true if the lock was granted, false if waitForLock was false and the lock could not be granted.
lockRecordForRead(Transaction
The transaction to associate the lock with.
t, ContainerHandle
Open Container used to get record. Will be used to row locks by the container they belong to.
container_handle, RecordHandle
The record to be locked.
record, boolean
Should lock request wait until granted?
waitForLock, boolean
Whether to open for read or write access.
forUpdate)

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

Implements org.apache.derby.iapi.store.raw.LockingPolicy.lockRecordForRead.

Obtain lock on record being read.

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

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

Implements org.apache.derby.iapi.store.raw.LockingPolicy.unlockRecordAfterRead.

Unlock a record after it has been locked for read.

Inherited from org.apache.derby.impl.store.raw.xact.RowLocking2:
lockContainerunlockContainer

Constructor Detail

RowLocking1back to summary
protected RowLocking1(LockFactory lf)

Method Detail

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

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

Implements org.apache.derby.iapi.store.raw.LockingPolicy.lockRecordForRead.

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.

Parameters
t:Transaction

The transaction to associate the lock with.

container_handle:ContainerHandle

Doc from org.apache.derby.iapi.store.raw.LockingPolicy.lockRecordForRead.

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

record:RecordHandle

The record to be locked.

waitForLock:boolean

Should lock request wait until granted?

forUpdate:boolean

Whether to open for read or write access.

Returns:boolean

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

Exceptions
StandardException:
Standard exception policy.
unlockRecordAfterReadback to summary
public void unlockRecordAfterRead(Transaction t, ContainerHandle container_handle, RecordHandle record, boolean forUpdate, boolean row_qualified) throws StandardException

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

Implements org.apache.derby.iapi.store.raw.LockingPolicy.unlockRecordAfterRead.

Doc from org.apache.derby.impl.store.raw.xact.RowLockingRR.unlockRecordAfterRead.

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.

Exceptions
StandardException:
Standard exception policy.