Class FSDirectory
- java.lang.Object
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- org.apache.lucene.store.Directory
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- org.apache.lucene.store.BaseDirectory
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- org.apache.lucene.store.FSDirectory
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
- Direct Known Subclasses:
MMapDirectory
,NIOFSDirectory
,SimpleFSDirectory
public abstract class FSDirectory extends BaseDirectory
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 usingThread.interrupt()
orFuture.cancel(boolean)
should useSimpleFSDirectory
instead. SeeNIOFSDirectory
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'sIndexInput.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 usingThread.interrupt()
orFuture.cancel(boolean)
should useSimpleFSDirectory
instead. SeeMMapDirectory
java doc for details.
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 useopen(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 customLockFactory
instance.- See Also:
Directory
-
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Nested Class Summary
Nested Classes Modifier and Type Class Description protected static class
FSDirectory.FSIndexInput
Base class for reading input from a RandomAccessFileprotected static class
FSDirectory.FSIndexOutput
Writes output withRandomAccessFile.write(byte[], int, int)
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Nested classes/interfaces inherited from class org.apache.lucene.store.Directory
Directory.IndexInputSlicer
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Field Summary
Fields Modifier and Type Field Description static int
DEFAULT_READ_CHUNK_SIZE
Deprecated.This constant is no longer used since Lucene 4.5.protected java.io.File
directory
protected java.util.Set<java.lang.String>
staleFiles
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Fields inherited from class org.apache.lucene.store.BaseDirectory
isOpen, lockFactory
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Constructor Summary
Constructors Modifier Constructor Description protected
FSDirectory(java.io.File path, LockFactory lockFactory)
Create a new FSDirectory for the named location (ctor for subclasses).
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description void
close()
Closes the store to future operations.IndexOutput
createOutput(java.lang.String name, IOContext context)
Creates an IndexOutput for the file with the given name.void
deleteFile(java.lang.String name)
Removes an existing file in the directory.protected void
ensureCanWrite(java.lang.String name)
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.protected void
fsync(java.lang.String name)
java.io.File
getDirectory()
java.lang.String
getLockID()
Return a string identifier that uniquely differentiates this Directory instance from other Directory instances.int
getReadChunkSize()
Deprecated.This is no longer used since Lucene 4.5.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.protected void
onIndexOutputClosed(FSDirectory.FSIndexOutput io)
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 likeopen(File)
, but allows you to also specify a customLockFactory
.void
setLockFactory(LockFactory lockFactory)
Set the LockFactory that this Directory instance should use for its locking implementation.void
setReadChunkSize(int chunkSize)
Deprecated.This is no longer used since Lucene 4.5.void
sync(java.util.Collection<java.lang.String> names)
Ensure that any writes to these files are moved to stable storage.java.lang.String
toString()
For debug output.-
Methods inherited from class org.apache.lucene.store.BaseDirectory
clearLock, ensureOpen, getLockFactory, makeLock
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Methods inherited from class org.apache.lucene.store.Directory
copy, createSlicer, openInput
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Field Detail
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DEFAULT_READ_CHUNK_SIZE
@Deprecated public static final int DEFAULT_READ_CHUNK_SIZE
Deprecated.This constant is no longer used since Lucene 4.5.Default read chunk size: 8192 bytes (this is the size up to which the JDK does not allocate additional arrays while reading/writing)- See Also:
- Constant Field Values
-
directory
protected final java.io.File directory
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staleFiles
protected final java.util.Set<java.lang.String> staleFiles
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Constructor Detail
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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 directorylockFactory
- the lock factory to use, or null for the default (NativeFSLockFactory
);- Throws:
java.io.IOException
- if there is a low-level I/O error
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Method Detail
-
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 theNativeFSLockFactory
.Currently this returns
MMapDirectory
for most Solaris and Windows 64-bit JREs,NIOFSDirectory
for other non-Windows JREs, andSimpleFSDirectory
for other JREs 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. For optimal performance you should consider using
MMapDirectory
on 64 bit JVMs.See above
- Throws:
java.io.IOException
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open
public static FSDirectory open(java.io.File path, LockFactory lockFactory) throws java.io.IOException
Just likeopen(File)
, but allows you to also specify a customLockFactory
.- Throws:
java.io.IOException
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setLockFactory
public void setLockFactory(LockFactory lockFactory) throws java.io.IOException
Description copied from class:Directory
Set the LockFactory that this Directory instance should use for its locking implementation. Each * instance of LockFactory should only be used for one directory (ie, do not share a single instance across multiple Directories).- Overrides:
setLockFactory
in classBaseDirectory
- Parameters:
lockFactory
- instance ofLockFactory
.- Throws:
java.io.IOException
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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 (throwsIOException
instead).- Throws:
NoSuchDirectoryException
- if the directory does not exist, or does exist but is not a directory.java.io.IOException
- if list() returns null
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listAll
public java.lang.String[] listAll() throws java.io.IOException
Lists all files (not subdirectories) in the directory.- Specified by:
listAll
in classDirectory
- Throws:
NoSuchDirectoryException
- if the directory is not prepared for any write operations (such asDirectory.createOutput(String, IOContext)
).java.io.IOException
- in case of other IO errors- See Also:
listAll(File)
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fileExists
public boolean fileExists(java.lang.String name)
Returns true iff a file with the given name exists.- Specified by:
fileExists
in classDirectory
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fileLength
public long fileLength(java.lang.String name) throws java.io.IOException
Returns the length in bytes of a file in the directory.- Specified by:
fileLength
in classDirectory
- Parameters:
name
- the name of the file for which to return the length.- Throws:
java.io.IOException
- if there was an IO error while retrieving the file's length.
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deleteFile
public void deleteFile(java.lang.String name) throws java.io.IOException
Removes an existing file in the directory.- Specified by:
deleteFile
in classDirectory
- Throws:
java.io.IOException
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createOutput
public IndexOutput createOutput(java.lang.String name, IOContext context) throws java.io.IOException
Creates an IndexOutput for the file with the given name.- Specified by:
createOutput
in classDirectory
- Throws:
java.io.IOException
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ensureCanWrite
protected void ensureCanWrite(java.lang.String name) throws java.io.IOException
- Throws:
java.io.IOException
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onIndexOutputClosed
protected void onIndexOutputClosed(FSDirectory.FSIndexOutput io)
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sync
public void sync(java.util.Collection<java.lang.String> names) throws java.io.IOException
Description copied from class:Directory
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.
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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.
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close
public void close()
Closes the store to future operations.
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getDirectory
public java.io.File getDirectory()
- Returns:
- the underlying filesystem directory
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toString
public java.lang.String toString()
For debug output.
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setReadChunkSize
@Deprecated public final void setReadChunkSize(int chunkSize)
Deprecated.This is no longer used since Lucene 4.5.This setting has no effect anymore.
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getReadChunkSize
@Deprecated public final int getReadChunkSize()
Deprecated.This is no longer used since Lucene 4.5.This setting has no effect anymore.
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fsync
protected void fsync(java.lang.String name) throws java.io.IOException
- Throws:
java.io.IOException
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