org.apache.derby.impl.io

Class VFMemoryStorageFactory

java.lang.Object

org.apache.derby.impl.io.VFMemoryStorageFactory

All Implemented Interfaces:

StorageFactory, WritableStorageFactory

public class VFMemoryStorageFactory
extends java.lang.Object
implements StorageFactory, WritableStorageFactory

A storage factory for virtual files, where the contents of the files are stored in main memory.

Note that data store deletion may happen inside one of two different methods; either in shutdown or in init. This is due to the current implementation and the fact that dropping a database is done through the file IO interface by deleting the service root. As the deletion then becomes a two step process, someone else may boot the database again before the reference to the store has been removed. To avoid this, the init-method will never initialize with a store scheduled for deletion. I have only seen this issue in heavily loaded multithreaded environments (2 CPUs/cores should be enough to reproduce).

Field Summary

Fields inherited from interface org.apache.derby.io.StorageFactory

VERSION_NUMBER

Constructor Summary

Constructors

Constructor and Description
VFMemoryStorageFactory() Creates a new, uninitialized instance of the storage factory.

Method Summary

Modifier and Type	Method and Description
StorageFile	createTemporaryFile(java.lang.String prefix, java.lang.String suffix) Creates a handle to a temporary file.
java.lang.String	getCanonicalName() Get the canonical name of the database.
char	getSeparator() Returns the path separator used by this storage factory.
int	getStorageFactoryVersion()
StorageFile	getTempDir() Returns the temporary directory for this storage factory instance.
void	init(java.lang.String home, java.lang.String databaseName, java.lang.String tempDirNameIgnored, java.lang.String uniqueName) Initializes the storage factory instance by setting up a temporary directory, the database directory and checking if the database being named already exists.
boolean	isFast() The service is fast and supports random access.
boolean	isReadOnlyDatabase() The service supports writes.
StorageFile	newStorageFile(StorageFile directoryName, java.lang.String fileName) Returns a handle to the specified storage file.
StorageFile	newStorageFile(java.lang.String path) Returns a handle to the specific storage file.
StorageFile	newStorageFile(java.lang.String directoryName, java.lang.String fileName) Returns a handle to the specified storage file.
void	setCanonicalName(java.lang.String name) Set the canonicalName.
void	shutdown() Normally does nothing, but if the database is in a state such that it should be deleted this will happen here.
boolean	supportsRandomAccess() The service supports random access.
boolean	supportsWriteSync() This method tests whether the StorageRandomAccessFile "rws" and "rwd" modes are implemented.
void	sync(java.io.OutputStream stream, boolean metaData) The sync method is a no-op for this storage factory.

Methods inherited from class java.lang.Object

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

Constructor Detail

VFMemoryStorageFactory

public VFMemoryStorageFactory()

Creates a new, uninitialized instance of the storage factory.

To initialize the instance, init must be called.

See Also:

init(java.lang.String, java.lang.String, java.lang.String, java.lang.String)

Method Detail

init

public void init(java.lang.String home,
                 java.lang.String databaseName,
                 java.lang.String tempDirNameIgnored,
                 java.lang.String uniqueName)
          throws java.io.IOException

Initializes the storage factory instance by setting up a temporary directory, the database directory and checking if the database being named already exists.

Specified by:

init in interface StorageFactory

Parameters:

home - the value of system.home for this storage factory

databaseName - the name of the database, all relative pathnames are relative to this name

tempDirNameIgnored - ignored

uniqueName - used to determine when the temporary directory can be created, but not to name the temporary directory itself

Throws:

java.io.IOException - on an error (unexpected).

shutdown

public void shutdown()

Normally does nothing, but if the database is in a state such that it should be deleted this will happen here.

Specified by:

shutdown in interface StorageFactory

getCanonicalName

public java.lang.String getCanonicalName()

Description copied from interface: StorageFactory

Get the canonical name of the database. This is a name that uniquely identifies it. It is system dependent. The normal, disk based implementation uses method java.io.File.getCanonicalPath on the directory holding the database to construct the canonical name.

Specified by:

getCanonicalName in interface StorageFactory

Returns:

the canonical name

setCanonicalName

public void setCanonicalName(java.lang.String name)

Set the canonicalName. May need adjustment due to DERBY-5096

Specified by:

setCanonicalName in interface StorageFactory

Parameters:

name - uniquely identifiable name for this database

newStorageFile

public StorageFile newStorageFile(java.lang.String path)

Returns a handle to the specific storage file.

Specified by:

newStorageFile in interface StorageFactory

Parameters:

path - the path of the file or directory

Returns:

A path handle.

newStorageFile

public StorageFile newStorageFile(java.lang.String directoryName,
                                  java.lang.String fileName)

Returns a handle to the specified storage file.

Specified by:

newStorageFile in interface StorageFactory

Parameters:

directoryName - the name of the parent directory

fileName - the name of the file

Returns:

A path handle.

newStorageFile

public StorageFile newStorageFile(StorageFile directoryName,
                                  java.lang.String fileName)

Returns a handle to the specified storage file.

Specified by:

newStorageFile in interface StorageFactory

Parameters:

directoryName - the name of the parent directory

fileName - the name of the file

Returns:

A path handle.

getTempDir

public StorageFile getTempDir()

Returns the temporary directory for this storage factory instance.

Specified by:

getTempDir in interface StorageFactory

Returns:

A StorageFile-object representing the temp directory.

isFast

public boolean isFast()

The service is fast and supports random access.

Specified by:

isFast in interface StorageFactory

Returns:

true

isReadOnlyDatabase

public boolean isReadOnlyDatabase()

The service supports writes.

Specified by:

isReadOnlyDatabase in interface StorageFactory

Returns:

false

supportsRandomAccess

public boolean supportsRandomAccess()

The service supports random access.

Specified by:

supportsRandomAccess in interface StorageFactory

Returns:

true

getStorageFactoryVersion

public int getStorageFactoryVersion()

Specified by:

getStorageFactoryVersion in interface StorageFactory

Returns:

the StorageFactory version supported by this implementation

createTemporaryFile

public StorageFile createTemporaryFile(java.lang.String prefix,
                                       java.lang.String suffix)

Creates a handle to a temporary file.

Specified by:

createTemporaryFile in interface StorageFactory

Parameters:

prefix - requested prefix for the file name

suffix - requested suffix for the file name, if null then .tmp will be used

Returns:

A handle to the temporary file.

getSeparator

public char getSeparator()

Returns the path separator used by this storage factory.

Specified by:

getSeparator in interface StorageFactory

Returns:

PathUtil.SEP

sync

public void sync(java.io.OutputStream stream,
                 boolean metaData)

The sync method is a no-op for this storage factory.

Specified by:

sync in interface WritableStorageFactory

Parameters:

stream - ignored

metaData - ignored

supportsWriteSync

public boolean supportsWriteSync()

Description copied from interface: WritableStorageFactory

This method tests whether the StorageRandomAccessFile "rws" and "rwd" modes are implemented. If the "rws" and "rwd" modes are supported then the database engine will conclude that the write methods of "rws"/"rwd" mode StorageRandomAccessFiles are slow but the sync method is fast and optimize accordingly.

Specified by:

supportsWriteSync in interface WritableStorageFactory

Returns:

true if an StIRandomAccess file opened with "rws" or "rwd" modes immediately writes data to the underlying storage, false if not.