Class RAMDirectory

A memory-resident Directory implementation. Locking implementation is by default the SingleInstanceLockFactory but can be changed with SetLockFactory(LockFactory).

Warning: This class is not intended to work with huge indexes. Everything beyond several hundred megabytes will waste resources (GC cycles), because it uses an internal buffer size of 1024 bytes, producing millions of byte[1024] arrays. This class is optimized for small memory-resident indexes. It also has bad concurrency on multithreaded environments.

It is recommended to materialize large indexes on disk and use MMapDirectory, which is a high-performance directory implementation working directly on the file system cache of the operating system, so copying data to heap space is not useful.
Inheritance
object
Directory
BaseDirectory
RAMDirectory
Implements
Inherited Members
Namespace: Lucene.Net.Store
Assembly: Lucene.Net.dll
Syntax
public class RAMDirectory : BaseDirectory, IDisposable

Constructors

RAMDirectory()

Constructs an empty Directory.

Declaration
public RAMDirectory()

RAMDirectory(Directory, IOContext)

Creates a new RAMDirectory instance from a different Directory implementation. This can be used to load a disk-based index into memory.

Warning: this class is not intended to work with huge indexes. Everything beyond several hundred megabytes will waste resources (GC cycles), because it uses an internal buffer size of 1024 bytes, producing millions of byte[1024] arrays. this class is optimized for small memory-resident indexes. It also has bad concurrency on multithreaded environments.

For disk-based indexes it is recommended to use MMapDirectory, which is a high-performance directory implementation working directly on the file system cache of the operating system, so copying data to heap space is not useful.

Note that the resulting RAMDirectory instance is fully independent from the original Directory (it is a complete copy). Any subsequent changes to the original Directory will not be visible in the RAMDirectory instance.
Declaration
public RAMDirectory(Directory dir, IOContext context)
Parameters
Type Name Description
Directory dir

a Directory value
IOContext context

io context
Exceptions
Type Condition
IOException

if an error occurs

Fields

m_fileMap

A memory-resident Directory implementation. Locking implementation is by default the SingleInstanceLockFactory but can be changed with SetLockFactory(LockFactory).

Warning: This class is not intended to work with huge indexes. Everything beyond several hundred megabytes will waste resources (GC cycles), because it uses an internal buffer size of 1024 bytes, producing millions of byte[1024] arrays. This class is optimized for small memory-resident indexes. It also has bad concurrency on multithreaded environments.

It is recommended to materialize large indexes on disk and use MMapDirectory, which is a high-performance directory implementation working directly on the file system cache of the operating system, so copying data to heap space is not useful.
Declaration
protected readonly ConcurrentDictionary<string, RAMFile> m_fileMap
Field Value
Type Description
ConcurrentDictionary<string, RAMFile>

m_sizeInBytes

A memory-resident Directory implementation. Locking implementation is by default the SingleInstanceLockFactory but can be changed with SetLockFactory(LockFactory).

Warning: This class is not intended to work with huge indexes. Everything beyond several hundred megabytes will waste resources (GC cycles), because it uses an internal buffer size of 1024 bytes, producing millions of byte[1024] arrays. This class is optimized for small memory-resident indexes. It also has bad concurrency on multithreaded environments.

It is recommended to materialize large indexes on disk and use MMapDirectory, which is a high-performance directory implementation working directly on the file system cache of the operating system, so copying data to heap space is not useful.
Declaration
protected readonly AtomicInt64 m_sizeInBytes
Field Value
Type Description
AtomicInt64

Methods

CreateOutput(string, IOContext)

Creates a new, empty file in the directory with the given name. Returns a stream writing this file.

Declaration
public override IndexOutput CreateOutput(string name, IOContext context)
Parameters
Type Name Description
string name
IOContext context
Returns
Type Description
IndexOutput
Overrides

DeleteFile(string)

Removes an existing file in the directory.

Declaration
public override void DeleteFile(string name)
Parameters
Type Name Description
string name
Overrides
Exceptions
Type Condition
IOException

if the file does not exist

Dispose(bool)

Closes the store to future operations, releasing associated memory.

Declaration
protected override void Dispose(bool disposing)
Parameters
Type Name Description
bool disposing
Overrides

FileExists(string)

Returns true iff the named file exists in this directory.

Declaration
[Obsolete("this method will be removed in 5.0")]
public override sealed bool FileExists(string name)
Parameters
Type Name Description
string name
Returns
Type Description
bool
Overrides

FileLength(string)

Returns the length in bytes of a file in the directory.

Declaration
public override sealed long FileLength(string name)
Parameters
Type Name Description
string name
Returns
Type Description
long
Overrides
Exceptions
Type Condition
IOException

if the file does not exist

GetLockID()

Return a string identifier that uniquely differentiates this Directory instance from other Directory instances. This ID should be the same if two Directory instances (even in different AppDomains and/or on different machines) are considered "the same index". This is how locking "scopes" to the right index.

Declaration
public override string GetLockID()
Returns
Type Description
string
Overrides

GetSizeInBytes()

Return total size in bytes of all files in this directory. This is currently quantized to BUFFER_SIZE.

Declaration
public long GetSizeInBytes()
Returns
Type Description
long

ListAll()

Returns an array of strings, one for each file in the directory.

Declaration
public override sealed string[] ListAll()
Returns
Type Description
string[]
Overrides
Exceptions
Type Condition
DirectoryNotFoundException

if the directory is not prepared for any write operations (such as CreateOutput(string, IOContext)).
IOException

in case of other IO errors

NewRAMFile()

Returns a new RAMFile for storing data. this method can be overridden to return different RAMFile impls, that e.g. override NewBuffer(int).

Declaration
protected virtual RAMFile NewRAMFile()
Returns
Type Description
RAMFile

OpenInput(string, IOContext)

Returns a stream reading an existing file.

Declaration
public override IndexInput OpenInput(string name, IOContext context)
Parameters
Type Name Description
string name
IOContext context
Returns
Type Description
IndexInput
Overrides

Sync(ICollection<string>)

Ensure that any writes to these files are moved to stable storage. Lucene uses this to properly commit changes to the index, to prevent a machine/OS crash from corrupting the index.

NOTE: Clients may call this method for same files over and over again, so some impls might optimize for that. For other impls the operation can be a noop, for various reasons.

Declaration
public override void Sync(ICollection<string> names)
Parameters
Type Name Description
ICollection<string> names
Overrides

Implements