Package org.h2.mvstore

Class Chunk<C extends Chunk<C>>

java.lang.Object
org.h2.mvstore.Chunk<C>
Direct Known Subclasses:
SFChunk
public abstract class Chunk<C extends Chunk<C>> extends 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
    Description
    static final class 
    Chunk.PositionComparator<C extends Chunk<C>>
     

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    long
    block
    The start block number within the file.
    ByteBuffer
    buffer
    ByteBuffer holding this Chunk's serialized content before it gets saved to file store.
    final int
    id
    The chunk id.
    int
    len
    The length in number of blocks.
    int
    mapId
    The last used map id.
    static final 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
    Description
    final String
    asString()
    Get the chunk metadata as a string to be stored in a layout map.
    protected void
    dump(StringBuilder buff)
     
    boolean
    equals(Object o)
     
    String
    getHeader()
     
    int
    hashCode()
     
    protected abstract ByteBuffer
    readFully(FileStore<C> fileStore, long filePos, int length)
     
    String
    toString()
     

    Methods inherited from class java.lang.Object

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

  • Field Details

    • MAX_ID

      public static final int MAX_ID
      The maximum chunk id.
      See Also:

    • 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 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 Details

    • readFully

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

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • asString

      public final String asString()
      Get the chunk metadata as a string to be stored in a layout map.
      Returns:
      the string

    • dump

      protected void dump(StringBuilder buff)

    • getHeader

      public String getHeader()

    • toString

      public String toString()
      Overrides:
      toString in class Object