org.h2.mvstore

Class Chunk<C extends Chunk<C>>

java.lang.Object

org.h2.mvstore.Chunk<C>

public abstract class Chunk<C extends Chunk<C>>
extends java.lang.Object

A chunk of data, containing one or multiple pages.

Minimum chunk size is usually 4096 bytes, and it grows in those fixed increments (blocks). Chunk's length and it's position in the underlying filestore are multiples of that increment (block size), therefore they both are measured in blocks, instead of bytes. There are at most 67 million (2^26) chunks, and each chunk is at most 2 GB large.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Chunk.PositionComparator<C extends Chunk<C>>

Field Summary

Fields

Modifier and Type	Field and Description
long	block The start block number within the file.
java.nio.ByteBuffer	buffer ByteBuffer holding this Chunk's serialized content before it gets saved to file store.
int	id The chunk id.
int	len The length in number of blocks.
int	mapId The last used map id.
static int	MAX_ID The maximum chunk id.
long	maxLen The sum of the max length of all pages.
long	maxLenLive The sum of the length of all pages that are still alive.
long	next The predicted position of the next chunk.
long	time When this chunk was created, in milliseconds since the store was created.
long	unused When this chunk was no longer needed, in milliseconds after the store was created.
long	version The version stored in this chunk.

Method Summary

Modifier and Type	Method and Description
java.lang.String	asString() Get the chunk metadata as a string to be stored in a layout map.
protected void	dump(java.lang.StringBuilder buff)
boolean	equals(java.lang.Object o)
java.lang.String	getHeader()
int	hashCode()
protected abstract java.nio.ByteBuffer	readFully(FileStore<C> fileStore, long filePos, int length)
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

MAX_ID

public static final int MAX_ID

The maximum chunk id.

See Also:

Constant Field Values

id

public final int id

The chunk id.

block

public volatile long block

The start block number within the file.

len

public int len

The length in number of blocks.

maxLen

public long maxLen

The sum of the max length of all pages.

maxLenLive

public long maxLenLive

The sum of the length of all pages that are still alive.

version

public long version

The version stored in this chunk.

time

public long time

When this chunk was created, in milliseconds since the store was created.

unused

public long unused

When this chunk was no longer needed, in milliseconds after the store was created. After this, the chunk is kept alive a bit longer (in case it is referenced in older versions).

mapId

public int mapId

The last used map id.

next

public long next

The predicted position of the next chunk.

buffer

public volatile java.nio.ByteBuffer buffer

ByteBuffer holding this Chunk's serialized content before it gets saved to file store. This allows to release pages of this Chunk earlier, allowing them to be garbage collected.

Method Detail

readFully

protected abstract java.nio.ByteBuffer readFully(FileStore<C> fileStore,
                                                 long filePos,
                                                 int length)

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

asString

public final java.lang.String asString()

Get the chunk metadata as a string to be stored in a layout map.

Returns:

the string

dump

protected void dump(java.lang.StringBuilder buff)

getHeader

public java.lang.String getHeader()

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object