Package org.h2.mvstore

Class FileStore

java.lang.Object

org.h2.mvstore.FileStore

Direct Known Subclasses:

OffHeapStore

public class FileStore
extends java.lang.Object

The default storage mechanism of the MVStore. This implementation persists data to a file. The file store is responsible to persist data and for free space management.

Field Summary

Fields

Modifier and Type	Field	Description
private java.nio.channels.FileChannel	encryptedFile	The encrypted file (if encryption is used).
private java.nio.channels.FileChannel	file	The file.
private java.nio.channels.FileLock	fileLock	The file lock.
private java.lang.String	fileName	The file name.
protected long	fileSize	The file size (cached).
protected FreeSpaceBitSet	freeSpace	The free spaces between the chunks.
protected java.util.concurrent.atomic.AtomicLong	readBytes	The number of read bytes.
protected java.util.concurrent.atomic.AtomicLong	readCount	The number of read operations.
private boolean	readOnly	Whether this store is read-only.
protected java.util.concurrent.atomic.AtomicLong	writeBytes	The number of written bytes.
protected java.util.concurrent.atomic.AtomicLong	writeCount	The number of write operations.

Constructor Summary

Constructors

Constructor	Description
FileStore()

Method Summary

Modifier and Type	Method	Description
(package private) long	allocate(int length, long reservedLow, long reservedHigh)	Allocate a number of blocks and mark them as used.
void	clear()	Mark the file as empty.
void	close()	Close this store.
void	free(long pos, int length)	Mark the space as free.
(package private) long	getAfterLastBlock()
int	getDefaultRetentionTime()	Get the default retention time for this store in milliseconds.
java.nio.channels.FileChannel	getEncryptedFile()	Get the encrypted file instance, if encryption is used.
java.nio.channels.FileChannel	getFile()	Get the file instance in use.
(package private) long	getFileLengthInUse()
java.lang.String	getFileName()	Get the file name.
int	getFillRate()
(package private) long	getFirstFree()
(package private) int	getMovePriority(int block)	Calculates relative "priority" for chunk to be moved.
int	getProjectedFillRate(int vacatedBlocks)	Calculates a prospective fill rate, which store would have after rewrite of sparsely populated chunk(s) and evacuation of still live data into a new chunk.
long	getReadBytes()	Get the number of read bytes since this store was opened.
long	getReadCount()	Get the number of read operations since this store was opened.
long	getWriteBytes()	Get the number of written bytes since this store was opened.
long	getWriteCount()	Get the number of write operations since this store was opened.
(package private) boolean	isFragmented()
boolean	isReadOnly()
void	markUsed(long pos, int length)	Mark the space as in use.
void	open(java.lang.String fileName, boolean readOnly, char[] encryptionKey)	Try to open the file.
(package private) long	predictAllocation(int blocks, long reservedLow, long reservedHigh)	Calculate starting position of the prospective allocation.
java.nio.ByteBuffer	readFully(long pos, int len)	Read from the file.
long	size()	Get the file size.
void	sync()	Flush all changes.
java.lang.String	toString()
void	truncate(long size)	Truncate the file.
void	writeFully(long pos, java.nio.ByteBuffer src)	Write to the file.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

readCount

protected final java.util.concurrent.atomic.AtomicLong readCount

The number of read operations.

readBytes

protected final java.util.concurrent.atomic.AtomicLong readBytes

The number of read bytes.

writeCount

protected final java.util.concurrent.atomic.AtomicLong writeCount

The number of write operations.

writeBytes

protected final java.util.concurrent.atomic.AtomicLong writeBytes

The number of written bytes.

freeSpace

protected final FreeSpaceBitSet freeSpace

The free spaces between the chunks. The first block to use is block 2 (the first two blocks are the store header).

fileName

private java.lang.String fileName

The file name.

readOnly

private boolean readOnly

Whether this store is read-only.

fileSize

protected long fileSize

The file size (cached).

file

private java.nio.channels.FileChannel file

The file.

encryptedFile

private java.nio.channels.FileChannel encryptedFile

The encrypted file (if encryption is used).

fileLock

private java.nio.channels.FileLock fileLock

The file lock.

Constructor Detail

FileStore

public FileStore()

Method Detail

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

readFully

public java.nio.ByteBuffer readFully(long pos,
                                     int len)

Read from the file.

Parameters:

pos - the write position

len - the number of bytes to read

Returns:

the byte buffer

writeFully

public void writeFully(long pos,
                       java.nio.ByteBuffer src)

Write to the file.

Parameters:

pos - the write position

src - the source buffer

open

public void open(java.lang.String fileName,
                 boolean readOnly,
                 char[] encryptionKey)

Try to open the file.

Parameters:

fileName - the file name

readOnly - whether the file should only be opened in read-only mode, even if the file is writable

encryptionKey - the encryption key, or null if encryption is not used

close

public void close()

Close this store.

sync

public void sync()

Flush all changes.

size

public long size()

Get the file size.

Returns:

the file size

truncate

public void truncate(long size)

Truncate the file.

Parameters:

size - the new file size

getFile

public java.nio.channels.FileChannel getFile()

Get the file instance in use.

The application may read from the file (for example for online backup), but not write to it or truncate it.

Returns:

the file

getEncryptedFile

public java.nio.channels.FileChannel getEncryptedFile()

Get the encrypted file instance, if encryption is used.

The application may read from the file (for example for online backup), but not write to it or truncate it.

Returns:

the encrypted file, or null if encryption is not used

getWriteCount

public long getWriteCount()

Get the number of write operations since this store was opened. For file based stores, this is the number of file write operations.

Returns:

the number of write operations

getWriteBytes

public long getWriteBytes()

Get the number of written bytes since this store was opened.

Returns:

the number of write operations

getReadCount

public long getReadCount()

Get the number of read operations since this store was opened. For file based stores, this is the number of file read operations.

Returns:

the number of read operations

getReadBytes

public long getReadBytes()

Get the number of read bytes since this store was opened.

Returns:

the number of write operations

isReadOnly

public boolean isReadOnly()

getDefaultRetentionTime

public int getDefaultRetentionTime()

Get the default retention time for this store in milliseconds.

Returns:

the retention time

markUsed

public void markUsed(long pos,
                     int length)

Mark the space as in use.

Parameters:

pos - the position in bytes

length - the number of bytes

allocate

long allocate(int length,
              long reservedLow,
              long reservedHigh)

Allocate a number of blocks and mark them as used.

Parameters:

length - the number of bytes to allocate

reservedLow - start block index of the reserved area (inclusive)

reservedHigh - end block index of the reserved area (exclusive), special value -1 means beginning of the infinite free area

Returns:

the start position in bytes

predictAllocation

long predictAllocation(int blocks,
                       long reservedLow,
                       long reservedHigh)

Calculate starting position of the prospective allocation.

Parameters:

blocks - the number of blocks to allocate

reservedLow - start block index of the reserved area (inclusive)

reservedHigh - end block index of the reserved area (exclusive), special value -1 means beginning of the infinite free area

Returns:

the starting block index

isFragmented

boolean isFragmented()

free

public void free(long pos,
                 int length)

Mark the space as free.

Parameters:

pos - the position in bytes

length - the number of bytes

getFillRate

public int getFillRate()

getProjectedFillRate

public int getProjectedFillRate(int vacatedBlocks)

Calculates a prospective fill rate, which store would have after rewrite of sparsely populated chunk(s) and evacuation of still live data into a new chunk.

Parameters:

vacatedBlocks - number of blocks vacated

Returns:

prospective fill rate (0 - 100)

getFirstFree

long getFirstFree()

getFileLengthInUse

long getFileLengthInUse()

getMovePriority

int getMovePriority(int block)

Calculates relative "priority" for chunk to be moved.

Parameters:

block - where chunk starts

Returns:

priority, bigger number indicate that chunk need to be moved sooner

getAfterLastBlock

long getAfterLastBlock()

clear

public void clear()

Mark the file as empty.

getFileName

public java.lang.String getFileName()

Get the file name.

Returns:

the file name