Class RAMDirectory
- 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.RAMDirectory
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- All Implemented Interfaces:
Closeable
,AutoCloseable
public class RAMDirectory extends BaseDirectory
A memory-residentDirectory
implementation. Locking implementation is by default theSingleInstanceLockFactory
but can be changed withBaseDirectory.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.
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Nested Class Summary
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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 protected Map<String,RAMFile>
fileMap
protected AtomicLong
sizeInBytes
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Fields inherited from class org.apache.lucene.store.BaseDirectory
isOpen, lockFactory
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Constructor Summary
Constructors Constructor Description RAMDirectory()
Constructs an emptyDirectory
.RAMDirectory(Directory dir, IOContext context)
Creates a newRAMDirectory
instance from a differentDirectory
implementation.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
close()
Closes the store to future operations, releasing associated memory.IndexOutput
createOutput(String name, IOContext context)
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.String
getLockID()
Return a string identifier that uniquely differentiates this Directory instance from other Directory instances.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, IOContext context)
Returns a stream reading an existing file.long
sizeInBytes()
Return total size in bytes of all files in this directory.void
sync(Collection<String> names)
Ensure that any writes to these files are moved to stable storage.-
Methods inherited from class org.apache.lucene.store.BaseDirectory
clearLock, ensureOpen, getLockFactory, makeLock, setLockFactory
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Methods inherited from class org.apache.lucene.store.Directory
copy, createSlicer, 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, IOContext context) 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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getLockID
public 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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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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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, IOContext context) 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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sync
public void sync(Collection<String> names) throws 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.- Specified by:
sync
in classDirectory
- Throws:
IOException
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openInput
public IndexInput openInput(String name, IOContext context) throws IOException
Returns a stream reading an existing file.- Specified by:
openInput
in classDirectory
- Throws:
IOException
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