Class RAMDirectory
- java.lang.Object
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- org.apache.lucene.store.Directory
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- org.apache.lucene.store.RAMDirectory
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- All Implemented Interfaces:
Closeable
,Serializable
,AutoCloseable
public class RAMDirectory extends Directory implements Serializable
A memory-residentDirectory
implementation. Locking implementation is by default theSingleInstanceLockFactory
but can be changed withDirectory.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
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Field Summary
Fields Modifier and Type Field Description protected Map<String,RAMFile>
fileMap
protected AtomicLong
sizeInBytes
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Fields inherited from class org.apache.lucene.store.Directory
isOpen, lockFactory
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Constructor Summary
Constructors Constructor Description RAMDirectory()
Constructs an emptyDirectory
.RAMDirectory(Directory dir)
Creates a newRAMDirectory
instance from a differentDirectory
implementation.
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Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description 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 newRAMFile
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
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Field Detail
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sizeInBytes
protected final AtomicLong sizeInBytes
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Constructor Detail
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RAMDirectory
public RAMDirectory()
Constructs an emptyDirectory
.
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RAMDirectory
public RAMDirectory(Directory dir) throws IOException
Creates a newRAMDirectory
instance from a differentDirectory
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 originalDirectory
(it is a complete copy). Any subsequent changes to the originalDirectory
will not be visible in theRAMDirectory
instance.- Parameters:
dir
- aDirectory
value- Throws:
IOException
- if an error occurs
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Method Detail
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listAll
public final String[] listAll()
Description copied from class:Directory
Returns an array of strings, one for each file in the directory.
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fileExists
public final boolean fileExists(String name)
Returns true iff the named file exists in this directory.- Specified by:
fileExists
in classDirectory
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fileModified
public final long fileModified(String name) throws IOException
Returns the time the named file was last modified.- Specified by:
fileModified
in classDirectory
- Throws:
IOException
- if the file does not exist
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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 classDirectory
- Throws:
IOException
- if the file does not exist
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fileLength
public final long fileLength(String name) throws 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:
IOException
- if the file does not exist
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sizeInBytes
public final long sizeInBytes()
Return total size in bytes of all files in this directory. This is currently quantized to RAMOutputStream.BUFFER_SIZE.
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deleteFile
public void deleteFile(String name) throws IOException
Removes an existing file in the directory.- Specified by:
deleteFile
in classDirectory
- Throws:
IOException
- if the file does not exist
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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 classDirectory
- Throws:
IOException
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newRAMFile
protected RAMFile newRAMFile()
Returns a newRAMFile
for storing data. This method can be overridden to return differentRAMFile
impls, that e.g. overrideRAMFile.newBuffer(int)
.
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openInput
public IndexInput openInput(String name) throws IOException
Returns a stream reading an existing file.- Specified by:
openInput
in classDirectory
- Throws:
IOException
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