Class MMapDirectory

File-based Directory implementation that uses for reading, and FSDirectory.FSIndexOutput for writing.

NOTE: memory mapping uses up a portion of the virtual memory address space in your process equal to the size of the file being mapped. Before using this class, be sure your have plenty of virtual address space, e.g. by using a 64 bit runtime, or a 32 bit runtime with indexes that are guaranteed to fit within the address space. On 32 bit platforms also consult MMapDirectory(DirectoryInfo, LockFactory, Int32) if you have problems with mmap failing because of fragmented address space. If you get an , it is recommended to reduce the chunk size, until it works.

NOTE: Accessing this class either directly or indirectly from a thread while it's interrupted can close the underlying channel immediately if at the same time the thread is blocked on IO. The channel will remain closed and subsequent access to MMapDirectory will throw a .

Inheritance
System.Object
Directory
BaseDirectory
FSDirectory
MMapDirectory
Inherited Members
Namespace: Lucene.Net.Store
Assembly: Lucene.Net.dll
Syntax
public class MMapDirectory : FSDirectory

Constructors

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MMapDirectory(DirectoryInfo)

Create a new MMapDirectory for the named location and NativeFSLockFactory.

Declaration
public MMapDirectory(DirectoryInfo path)
Parameters
Type Name Description
DirectoryInfo path

the path of the directory

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MMapDirectory(DirectoryInfo, LockFactory)

Create a new MMapDirectory for the named location.

Declaration
public MMapDirectory(DirectoryInfo path, LockFactory lockFactory)
Parameters
Type Name Description
DirectoryInfo path

the path of the directory

LockFactory lockFactory

the lock factory to use, or null for the default (NativeFSLockFactory);

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MMapDirectory(DirectoryInfo, LockFactory, Int32)

Create a new MMapDirectory for the named location, specifying the maximum chunk size used for memory mapping.

Declaration
public MMapDirectory(DirectoryInfo path, LockFactory lockFactory, int maxChunkSize)
Parameters
Type Name Description
DirectoryInfo path

the path of the directory

LockFactory lockFactory

the lock factory to use, or null for the default (NativeFSLockFactory);

System.Int32 maxChunkSize

maximum chunk size (default is 1 GiBytes for 64 bit runtimes and 256 MiBytes for 32 bit runtimes) used for memory mapping.

Especially on 32 bit platform, the address space can be very fragmented, so large index files cannot be mapped. Using a lower chunk size makes the directory implementation a little bit slower (as the correct chunk may be resolved on lots of seeks) but the chance is higher that mmap does not fail. On 64 bit platforms, this parameter should always be 1 << 30, as the address space is big enough.

Please note: The chunk size is always rounded down to a power of 2.
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MMapDirectory(String)

Create a new MMapDirectory for the named location and NativeFSLockFactory.

LUCENENET specific overload for convenience using string instead of .

Declaration
public MMapDirectory(string path)
Parameters
Type Name Description
System.String path

the path of the directory

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MMapDirectory(String, LockFactory)

Create a new MMapDirectory for the named location.

LUCENENET specific overload for convenience using string instead of .

Declaration
public MMapDirectory(string path, LockFactory lockFactory)
Parameters
Type Name Description
System.String path

the path of the directory

LockFactory lockFactory

the lock factory to use, or null for the default (NativeFSLockFactory);

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MMapDirectory(String, LockFactory, Int32)

Create a new MMapDirectory for the named location, specifying the maximum chunk size used for memory mapping.

LUCENENET specific overload for convenience using string instead of .

Declaration
public MMapDirectory(string path, LockFactory lockFactory, int maxChunkSize)
Parameters
Type Name Description
System.String path

the path of the directory

LockFactory lockFactory

the lock factory to use, or null for the default (NativeFSLockFactory);

System.Int32 maxChunkSize

maximum chunk size (default is 1 GiBytes for 64 bit runtimes and 256 MiBytes for 32 bit runtimes) used for memory mapping.

Especially on 32 bit platform, the address space can be very fragmented, so large index files cannot be mapped. Using a lower chunk size makes the directory implementation a little bit slower (as the correct chunk may be resolved on lots of seeks) but the chance is higher that mmap does not fail. On 64 bit platforms, this parameter should always be 1 << 30, as the address space is big enough.

Please note: The chunk size is always rounded down to a power of 2.

Fields

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DEFAULT_MAX_BUFF

Default max chunk size.

Declaration
public static readonly int DEFAULT_MAX_BUFF
Field Value
Type Description
System.Int32
See Also

Properties

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MaxChunkSize

Returns the current mmap chunk size.

Declaration
public int MaxChunkSize { get; }
Property Value
Type Description
System.Int32
See Also

Methods

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CreateSlicer(String, IOContext)

Declaration
public override Directory.IndexInputSlicer CreateSlicer(string name, IOContext context)
Parameters
Type Name Description
System.String name
IOContext context
Returns
Type Description
Directory.IndexInputSlicer
Overrides
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OpenInput(String, IOContext)

Creates an IndexInput for the file with the given name.

Declaration
public override IndexInput OpenInput(string name, IOContext context)
Parameters
Type Name Description
System.String name
IOContext context
Returns
Type Description
IndexInput
Overrides