FSDirectory (Lucene 2.9.4 API)

java.lang.Object
- org.apache.lucene.store.Directory
- - org.apache.lucene.store.FSDirectory

Direct Known Subclasses:

MMapDirectory, NIOFSDirectory, SimpleFSDirectory
```
public class FSDirectory
extends Directory
```
Base class for Directory implementations that store index files in the file system. There are currently three core subclasses:
- SimpleFSDirectory is a straightforward implementation using java.io.RandomAccessFile. However, it has poor concurrent performance (multiple threads will bottleneck) as it synchronizes when multiple threads read from the same file.
- NIOFSDirectory uses java.nio's FileChannel's positional io when reading to avoid synchronization when reading from the same file. Unfortunately, due to a Windows-only Sun JRE bug this is a poor choice for Windows, but on all other platforms this is the preferred choice. Applications using Thread.interrupt() or Future#cancel(boolean) (on Java 1.5) should use SimpleFSDirectory instead. See NIOFSDirectory java doc for details.
- MMapDirectory uses memory-mapped IO when reading. This is a good choice if you have plenty of virtual memory relative to your index size, eg if you are running on a 64 bit JRE, or you are running on a 32 bit JRE but your index sizes are small enough to fit into the virtual memory space. Java has currently the limitation of not being able to unmap files from user code. The files are unmapped, when GC releases the byte buffers. Due to this bug in Sun's JRE, MMapDirectory's IndexInput.close() is unable to close the underlying OS file handle. Only when GC finally collects the underlying objects, which could be quite some time later, will the file handle be closed. This will consume additional transient disk usage: on Windows, attempts to delete or overwrite the files will result in an exception; on other platforms, which typically have a "delete on last close" semantics, while such operations will succeed, the bytes are still consuming space on disk. For many applications this limitation is not a problem (e.g. if you have plenty of disk space, and you don't rely on overwriting files on Windows) but it's still an important limitation to be aware of. This class supplies a (possibly dangerous) workaround mentioned in the bug report, which may fail on non-Sun JVMs. Applications using Thread.interrupt() or Future#cancel(boolean) (on Java 1.5) should use SimpleFSDirectory instead. See MMapDirectory java doc for details.
Unfortunately, because of system peculiarities, there is no single overall best implementation. Therefore, we've added the open(java.io.File) method, to allow Lucene to choose the best FSDirectory implementation given your environment, and the known limitations of each implementation. For users who have no reason to prefer a specific implementation, it's best to simply use open(java.io.File). For all others, you should instantiate the desired implementation directly.
The locking implementation is by default NativeFSLockFactory, but can be changed by passing in a custom LockFactory instance. The deprecated getDirectory methods default to use SimpleFSLockFactory for backwards compatibility. The system properties org.apache.lucene.store.FSDirectoryLockFactoryClass and org.apache.lucene.FSDirectory.class are deprecated and only used by the deprecated getDirectory methods. The system property org.apache.lucene.lockDir is ignored completely, If you really want to store locks elsewhere, you can create your own SimpleFSLockFactory (or NativeFSLockFactory, etc.) passing in your preferred lock directory.
In 3.0 this class will become abstract.
See Also:

Directory

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`protected static class`	`FSDirectory.FSIndexInput` Deprecated. Use SimpleFSDirectory.SimpleFSIndexInput instead
`protected static class`	`FSDirectory.FSIndexOutput` Deprecated. Use SimpleFSDirectory.SimpleFSIndexOutput instead

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`DEFAULT_READ_CHUNK_SIZE` Default read chunk size.
`protected java.io.File`	`directory` The underlying filesystem directory
`static java.lang.String`	`LOCK_DIR` Deprecated. As of 2.1, `LOCK_DIR` is unused because the write.lock is now stored by default in the index directory. If you really want to store locks elsewhere, you can create your own `SimpleFSLockFactory` (or `NativeFSLockFactory`, etc.) passing in your preferred lock directory. Then, pass this `LockFactory` instance to one of the `open` methods that take a `lockFactory` (for example, `open(File, LockFactory)`).

Fields inherited from class org.apache.lucene.store.Directory
isOpen, lockFactory

Constructor Summary

Constructors
Modifier	Constructor and Description
`protected`	`FSDirectory()` Deprecated.
`protected`	`FSDirectory(java.io.File path, LockFactory lockFactory)` Create a new FSDirectory for the named location (ctor for subclasses).

Method Summary

All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`void`	`close()` Closes the store to future operations.
`IndexOutput`	`createOutput(java.lang.String name)` Creates an IndexOutput for the file with the given name.
`void`	`deleteFile(java.lang.String name)` Removes an existing file in the directory.
`boolean`	`fileExists(java.lang.String name)` Returns true iff a file with the given name exists.
`long`	`fileLength(java.lang.String name)` Returns the length in bytes of a file in the directory.
`static long`	`fileModified(java.io.File directory, java.lang.String name)` Returns the time the named file was last modified.
`long`	`fileModified(java.lang.String name)` Returns the time the named file was last modified.
`static FSDirectory`	`getDirectory(java.io.File file)` Deprecated. Use `open(File)`
`static FSDirectory`	`getDirectory(java.io.File file, boolean create)` Deprecated. Use IndexWriter's create flag, instead, to create a new index.
`static FSDirectory`	`getDirectory(java.io.File file, LockFactory lockFactory)` Deprecated. Use `open(File, LockFactory)`
`static FSDirectory`	`getDirectory(java.lang.String path)` Deprecated. Use `open(File)`
`static FSDirectory`	`getDirectory(java.lang.String path, boolean create)` Deprecated. Use IndexWriter's create flag, instead, to create a new index.
`static FSDirectory`	`getDirectory(java.lang.String path, LockFactory lockFactory)` Deprecated. Use `open(File, LockFactory)`
`static boolean`	`getDisableLocks()` Deprecated. Use a constructor that takes a `LockFactory` and supply `NoLockFactory.getNoLockFactory()`.
`java.io.File`	`getFile()`
`java.lang.String`	`getLockID()` Return a string identifier that uniquely differentiates this Directory instance from other Directory instances.
`int`	`getReadChunkSize()` The maximum number of bytes to read at once from the underlying file during `IndexInput.readBytes(byte[], int, int)`.
`protected void`	`initOutput(java.lang.String name)` Initializes the directory to create a new file with the given name.
`java.lang.String[]`	`list()` List the files in the directory.
`java.lang.String[]`	`listAll()` Lists all files (not subdirectories) in the directory.
`static java.lang.String[]`	`listAll(java.io.File dir)` Lists all files (not subdirectories) in the directory.
`static FSDirectory`	`open(java.io.File path)` Creates an FSDirectory instance, trying to pick the best implementation given the current environment.
`static FSDirectory`	`open(java.io.File path, LockFactory lockFactory)` Just like `open(File)`, but allows you to also specify a custom `LockFactory`.
`IndexInput`	`openInput(java.lang.String name)` Returns a stream reading an existing file.
`IndexInput`	`openInput(java.lang.String name, int bufferSize)` Creates an IndexInput for the file with the given name.
`void`	`renameFile(java.lang.String from, java.lang.String to)` Deprecated.
`static void`	`setDisableLocks(boolean doDisableLocks)` Deprecated. Use a `open(File, LockFactory)` or a constructor that takes a `LockFactory` and supply `NoLockFactory.getNoLockFactory()`. This setting does not work with `open(File)` only the deprecated `getDirectory` respect this setting.
`void`	`setReadChunkSize(int chunkSize)` Sets the maximum number of bytes read at once from the underlying file during `IndexInput.readBytes(byte[], int, int)`.
`void`	`sync(java.lang.String name)` Ensure that any writes to this file are moved to stable storage.
`java.lang.String`	`toString()` For debug output.
`void`	`touchFile(java.lang.String name)` Set the modified time of an existing file to now.

Methods inherited from class org.apache.lucene.store.Directory
clearLock, copy, ensureOpen, getLockFactory, makeLock, setLockFactory

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - LOCK_DIR
```
public static final java.lang.String LOCK_DIR
```
    Deprecated. As of 2.1, LOCK_DIR is unused because the write.lock is now stored by default in the index directory. If you really want to store locks elsewhere, you can create your own SimpleFSLockFactory (or NativeFSLockFactory, etc.) passing in your preferred lock directory. Then, pass this LockFactory instance to one of the open methods that take a lockFactory (for example, open(File, LockFactory)).
    
    Directory specified by org.apache.lucene.lockDir or java.io.tmpdir system property.
  - directory
```
protected java.io.File directory
```
    The underlying filesystem directory
  - DEFAULT_READ_CHUNK_SIZE
```
public static final int DEFAULT_READ_CHUNK_SIZE
```
    Default read chunk size. This is a conditional default: on 32bit JVMs, it defaults to 100 MB. On 64bit JVMs, it's Integer.MAX_VALUE.
    
    See Also:
    
    setReadChunkSize(int)
- Constructor Detail
  - FSDirectory
```
protected FSDirectory()
```
    Deprecated.
  - FSDirectory
```
protected FSDirectory(java.io.File path,
                      LockFactory lockFactory)
               throws java.io.IOException
```
    Create a new FSDirectory for the named location (ctor for subclasses).
    
    Parameters:
    
    path - the path of the directory
    
    lockFactory - the lock factory to use, or null for the default (NativeFSLockFactory);
    
    Throws:
    
    java.io.IOException
- Method Detail
  - setDisableLocks
```
public static void setDisableLocks(boolean doDisableLocks)
```
    Deprecated. Use a open(File, LockFactory) or a constructor that takes a LockFactory and supply NoLockFactory.getNoLockFactory(). This setting does not work with open(File) only the deprecated getDirectory respect this setting.
    
    Set whether Lucene's use of lock files is disabled. By default, lock files are enabled. They should only be disabled if the index is on a read-only medium like a CD-ROM.
  - getDisableLocks
```
public static boolean getDisableLocks()
```
    Deprecated. Use a constructor that takes a LockFactory and supply NoLockFactory.getNoLockFactory().
    
    Returns whether Lucene's use of lock files is disabled.
    
    Returns:
    
    true if locks are disabled, false if locks are enabled.
    
    See Also:
    
    setDisableLocks(boolean)
  - getDirectory
```
public static FSDirectory getDirectory(java.lang.String path)
                                throws java.io.IOException
```
    Deprecated. Use open(File)
    
    Returns the directory instance for the named location.
    
    Parameters:
    
    path - the path to the directory.
    
    Returns:
    
    the FSDirectory for the named file.
    
    Throws:
    
    java.io.IOException
  - getDirectory
```
public static FSDirectory getDirectory(java.lang.String path,
                                       LockFactory lockFactory)
                                throws java.io.IOException
```
    Deprecated. Use open(File, LockFactory)
    
    Returns the directory instance for the named location.
    
    Parameters:
    
    path - the path to the directory.
    
    lockFactory - instance of LockFactory providing the locking implementation.
    
    Returns:
    
    the FSDirectory for the named file.
    
    Throws:
    
    java.io.IOException
  - getDirectory
```
public static FSDirectory getDirectory(java.io.File file)
                                throws java.io.IOException
```
    Deprecated. Use open(File)
    
    Returns the directory instance for the named location.
    
    Parameters:
    
    file - the path to the directory.
    
    Returns:
    
    the FSDirectory for the named file.
    
    Throws:
    
    java.io.IOException
  - getDirectory
```
public static FSDirectory getDirectory(java.io.File file,
                                       LockFactory lockFactory)
                                throws java.io.IOException
```
    Deprecated. Use open(File, LockFactory)
    
    Returns the directory instance for the named location.
    
    Parameters:
    
    file - the path to the directory.
    
    lockFactory - instance of LockFactory providing the locking implementation.
    
    Returns:
    
    the FSDirectory for the named file.
    
    Throws:
    
    java.io.IOException
  - getDirectory
```
public static FSDirectory getDirectory(java.lang.String path,
                                       boolean create)
                                throws java.io.IOException
```
    Deprecated. Use IndexWriter's create flag, instead, to create a new index.
    
    Returns the directory instance for the named location.
    
    Parameters:
    
    path - the path to the directory.
    
    create - if true, create, or erase any existing contents.
    
    Returns:
    
    the FSDirectory for the named file.
    
    Throws:
    
    java.io.IOException
  - getDirectory
```
public static FSDirectory getDirectory(java.io.File file,
                                       boolean create)
                                throws java.io.IOException
```
    Deprecated. Use IndexWriter's create flag, instead, to create a new index.
    
    Returns the directory instance for the named location.
    
    Parameters:
    
    file - the path to the directory.
    
    create - if true, create, or erase any existing contents.
    
    Returns:
    
    the FSDirectory for the named file.
    
    Throws:
    
    java.io.IOException
  - initOutput
```
protected final void initOutput(java.lang.String name)
                         throws java.io.IOException
```
    Initializes the directory to create a new file with the given name. This method should be used in createOutput(java.lang.String).
    
    Throws:
    
    java.io.IOException
  - open
```
public static FSDirectory open(java.io.File path)
                        throws java.io.IOException
```
    Creates an FSDirectory instance, trying to pick the best implementation given the current environment. The directory returned uses the NativeFSLockFactory.
    Currently this returns NIOFSDirectory on non-Windows JREs and SimpleFSDirectory on Windows. It is highly recommended that you consult the implementation's documentation for your platform before using this method.
    NOTE: this method may suddenly change which implementation is returned from release to release, in the event that higher performance defaults become possible; if the precise implementation is important to your application, please instantiate it directly, instead. On 64 bit systems, it may also good to return MMapDirectory, but this is disabled because of officially missing unmap support in Java. For optimal performance you should consider using this implementation on 64 bit JVMs.
    See above
    
    Throws:
    
    java.io.IOException
  - open
```
public static FSDirectory open(java.io.File path,
                               LockFactory lockFactory)
                        throws java.io.IOException
```
    Just like open(File), but allows you to also specify a custom LockFactory.
    
    Throws:
    
    java.io.IOException
  - listAll
```
public static java.lang.String[] listAll(java.io.File dir)
                                  throws java.io.IOException
```
    Lists all files (not subdirectories) in the directory. This method never returns null (throws IOException instead).
    
    Throws:
    
    NoSuchDirectoryException - if the directory does not exist, or does exist but is not a directory.
    
    java.io.IOException - if list() returns null
  - list
```
public java.lang.String[] list()
```
    Description copied from class: Directory
    
    List the files in the directory.
    
    Specified by:
    
    list in class Directory
  - listAll
```
public java.lang.String[] listAll()
                           throws java.io.IOException
```
    Lists all files (not subdirectories) in the directory.
    
    Overrides:
    
    listAll in class Directory
    
    Throws:
    
    java.io.IOException
    
    See Also:
    
    listAll(File)
  - fileExists
```
public boolean fileExists(java.lang.String name)
```
    Returns true iff a file with the given name exists.
    
    Specified by:
    
    fileExists in class Directory
  - fileModified
```
public long fileModified(java.lang.String name)
```
    Returns the time the named file was last modified.
    
    Specified by:
    
    fileModified in class Directory
  - fileModified
```
public static long fileModified(java.io.File directory,
                                java.lang.String name)
```
    Returns the time the named file was last modified.
  - touchFile
```
public void touchFile(java.lang.String name)
```
    Set the modified time of an existing file to now.
    
    Specified by:
    
    touchFile in class Directory
  - fileLength
```
public long fileLength(java.lang.String name)
```
    Returns the length in bytes of a file in the directory.
    
    Specified by:
    
    fileLength in class Directory
  - deleteFile
```
public void deleteFile(java.lang.String name)
                throws java.io.IOException
```
    Removes an existing file in the directory.
    
    Specified by:
    
    deleteFile in class Directory
    
    Throws:
    
    java.io.IOException
  - renameFile
```
public void renameFile(java.lang.String from,
                       java.lang.String to)
                throws java.io.IOException
```
    Deprecated.
    
    Renames an existing file in the directory. Warning: This is not atomic.
    
    Specified by:
    
    renameFile in class Directory
    
    Throws:
    
    java.io.IOException
  - createOutput
```
public IndexOutput createOutput(java.lang.String name)
                         throws java.io.IOException
```
    Creates an IndexOutput for the file with the given name. In 3.0 this method will become abstract.
    
    Specified by:
    
    createOutput in class Directory
    
    Throws:
    
    java.io.IOException
  - sync
```
public void sync(java.lang.String name)
          throws java.io.IOException
```
    Description copied from class: Directory
    
    Ensure that any writes to this file 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.
    
    Overrides:
    
    sync in class Directory
    
    Throws:
    
    java.io.IOException
  - openInput
```
public IndexInput openInput(java.lang.String name)
                     throws java.io.IOException
```
    Description copied from class: Directory
    
    Returns a stream reading an existing file.
    
    Specified by:
    
    openInput in class Directory
    
    Throws:
    
    java.io.IOException
  - openInput
```
public IndexInput openInput(java.lang.String name,
                            int bufferSize)
                     throws java.io.IOException
```
    Creates an IndexInput for the file with the given name. In 3.0 this method will become abstract.
    
    Overrides:
    
    openInput in class Directory
    
    Throws:
    
    java.io.IOException
  - getLockID
```
public java.lang.String getLockID()
```
    Description copied from class: Directory
    
    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 JVMs and/or on different machines) are considered "the same index". This is how locking "scopes" to the right index.
    
    Overrides:
    
    getLockID in class Directory
  - close
```
public void close()
```
    Closes the store to future operations.
    
    Specified by:
    
    close in class Directory
  - getFile
```
public java.io.File getFile()
```
  - toString
```
public java.lang.String toString()
```
    For debug output.
    
    Overrides:
    
    toString in class Directory
  - setReadChunkSize
```
public final void setReadChunkSize(int chunkSize)
```
    Sets the maximum number of bytes read at once from the underlying file during IndexInput.readBytes(byte[], int, int). The default value is DEFAULT_READ_CHUNK_SIZE;
    This was introduced due to Sun JVM Bug 6478546, which throws an incorrect OutOfMemoryError when attempting to read too many bytes at once. It only happens on 32bit JVMs with a large maximum heap size.
    
    Changes to this value will not impact any already-opened IndexInputs. You should call this before attempting to open an index on the directory.
    
    NOTE: This value should be as large as possible to reduce any possible performance impact. If you still encounter an incorrect OutOfMemoryError, trying lowering the chunk size.
  - getReadChunkSize
```
public final int getReadChunkSize()
```
    The maximum number of bytes to read at once from the underlying file during IndexInput.readBytes(byte[], int, int).
    
    See Also:
    
    setReadChunkSize(int)

Class FSDirectory

Nested Class Summary

Field Summary

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

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Field Detail

LOCK_DIR

directory

DEFAULT_READ_CHUNK_SIZE

Constructor Detail

FSDirectory

FSDirectory

Method Detail

setDisableLocks

getDisableLocks

getDirectory

getDirectory

getDirectory

getDirectory

getDirectory

getDirectory

initOutput

open

open

listAll

list

listAll

fileExists

fileModified

fileModified

touchFile

fileLength

deleteFile

renameFile

createOutput

sync

openInput

openInput

getLockID

close

getFile

toString

setReadChunkSize

getReadChunkSize