org.apache.lucene.store
Class RAMDirectory

java.lang.Object
  org.apache.lucene.store.Directory
      org.apache.lucene.store.RAMDirectory

All Implemented Interfaces:

Closeable, Serializable

public class RAMDirectory
extends Directory
implements Serializable

A memory-resident Directory implementation. Locking implementation is by default the SingleInstanceLockFactory but can be changed with Directory.setLockFactory(org.apache.lucene.store.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 Java heap space is not useful.

See Also:

Serialized Form

Field Summary

protected Map<String,RAMFile>	fileMap
protected AtomicLong	sizeInBytes

Fields inherited from class org.apache.lucene.store.Directory

isOpen, lockFactory

Constructor Summary

RAMDirectory()
Constructs an empty Directory.

RAMDirectory(Directory dir)
Creates a new RAMDirectory instance from a different Directory implementation.

Method Summary

void	close() Closes the store to future operations, releasing associated memory.
IndexOutput	createOutput(String name) Creates a new, empty file in the directory with the given name.
void	deleteFile(String name) Removes an existing file in the directory.
boolean	fileExists(String name) Returns true iff the named file exists in this directory.
long	fileLength(String name) Returns the length in bytes of a file in the directory.
long	fileModified(String name) Returns the time the named file was last modified.
String[]	listAll() Returns an array of strings, one for each file in the directory.
protected RAMFile	newRAMFile() Returns a new RAMFile for storing data.
IndexInput	openInput(String name) Returns a stream reading an existing file.
long	sizeInBytes() Return total size in bytes of all files in this directory.
void	touchFile(String name) Deprecated. Lucene never uses this API; it will be removed in 4.0.

Methods inherited from class org.apache.lucene.store.Directory

clearLock, copy, copy, ensureOpen, getLockFactory, getLockID, makeLock, openInput, setLockFactory, sync, sync, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

fileMap

protected final Map<String,RAMFile> fileMap

sizeInBytes

protected final AtomicLong sizeInBytes

Constructor Detail

RAMDirectory

public RAMDirectory()

Constructs an empty Directory.

RAMDirectory

public RAMDirectory(Directory dir)
             throws IOException

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 Java 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.

Parameters:

dir - a Directory value

Throws:

IOException - if an error occurs

Method Detail

listAll

public final String[] listAll()

Description copied from class: Directory

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

Specified by:

listAll in class Directory

fileExists

public final boolean fileExists(String name)

Returns true iff the named file exists in this directory.

Specified by:

fileExists in class Directory

fileModified

public final long fileModified(String name)
                        throws IOException

Returns the time the named file was last modified.

Specified by:

fileModified in class Directory

Throws:

IOException - if the file does not exist

touchFile

@Deprecated
public void touchFile(String name)
               throws IOException

Deprecated. Lucene never uses this API; it will be removed in 4.0.

Set the modified time of an existing file to now.

Specified by:

touchFile in class Directory

Throws:

IOException - if the file does not exist

fileLength

public final long fileLength(String name)
                      throws IOException

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

Specified by:

fileLength in class Directory

Parameters:

name - the name of the file for which to return the length.

Throws:

IOException - if the file does not exist

sizeInBytes

public final long sizeInBytes()

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

deleteFile

public void deleteFile(String name)
                throws IOException

Removes an existing file in the directory.

Specified by:

deleteFile in class Directory

Throws:

IOException - if the file does not exist

createOutput

public IndexOutput createOutput(String name)
                         throws IOException

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

Specified by:

createOutput in class Directory

Throws:

IOException

newRAMFile

protected RAMFile newRAMFile()

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

openInput

public IndexInput openInput(String name)
                     throws IOException

Returns a stream reading an existing file.

Specified by:

openInput in class Directory

Throws:

IOException

close

public void close()

Closes the store to future operations, releasing associated memory.

Specified by:

close in interface Closeable

Specified by:

close in class Directory