Package org.h2.mvstore

Class Page<K,V>

java.lang.Object
org.h2.mvstore.Page<K,V>
All Implemented Interfaces:
Cloneable
public abstract class Page<K,V> extends Object implements Cloneable
A page (a node or a leaf).

For b-tree nodes, the key at a given index is larger than the largest key of the child at the same index.

Serialized format: length of a serialized page in bytes (including this field): int check value: short page number (0-based sequential number within a chunk): varInt map id: varInt number of keys: varInt type: byte (0: leaf, 1: node; +2: compressed) children of the non-leaf node (1 more than keys) compressed: bytes saved (varInt) keys values of the leaf node (one for each key)

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static final class 
    Page.PageReference<K,V>
    A pointer to a page, either in-memory or using a page position.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    final MVMap<K,V>
    map
    Map this page belongs to
    int
    pageNo
    Sequential 0-based number of the page within containing chunk.

  • Method Summary

    Modifier and Type
    Method
    Description
    protected int
    calculateMemory()
    Calculate estimated memory used in persistent case.
    protected final Page<K,V>
    clone()
     
    final Page<K,V>
    copy()
    Create a copy of this page.
    final K[]
    createKeyStorage(int size)
    Create array for keys storage.
    static <K, V> Page<K,V>
    createNode(MVMap<K,V> map, K[] keys, Page.PageReference<K,V>[] children, long totalCount, int memory)
    Create a new non-leaf page.
    static <K, V> Page.PageReference<K,V>[]
    createRefStorage(int size)
    Create an array of page references.
    protected void
    dump(StringBuilder buff)
    Dump debug data for this page.
    abstract CursorPos<K,V>
    getAppendCursorPos(CursorPos<K,V> cursorPos)
    Extend path from a given CursorPos chain to "append point" in a B-tree, rooted at this Page.
    abstract Page<K,V>
    getChildPage(int index)
    Get the child page at the given index.
    abstract long
    getChildPagePos(int index)
    Get the position of the child.
    final long
    getDiskSpaceUsed(boolean approximate)
    Amount of used disk space in persistent case including child pages.
    K
    getKey(int index)
    Get the key at the given index.
    final int
    getKeyCount()
    Get the number of keys in this page.
    final int
    getMapId()
    Get the id of the page's owner map
    final int
    getMemory()
     
    abstract int
    getNodeType()
     
    final long
    getPos()
    Get the position of the page
    abstract CursorPos<K,V>
    getPrependCursorPos(CursorPos<K,V> cursorPos)
    Extend path from a given CursorPos chain to "prepend point" in a B-tree, rooted at this Page.
    abstract int
    getRawChildPageCount()
     
    abstract long
    getTotalCount()
    Get the total number of key-value pairs, including child pages.
    abstract V
    getValue(int index)
    Get the value at the given index.
    abstract void
    insertLeaf(int index, K key, V value)
    Insert a key-value pair into this leaf.
    abstract void
    insertNode(int index, K key, Page<K,V> childPage)
    Insert a child page into this node.
    boolean
    isComplete()
     
    final boolean
    isLeaf()
    Check whether this is a leaf page.
    protected final boolean
    isPersistent()
     
    final boolean
    isRemoved()
     
    final boolean
    isSaved()
     
    protected abstract void
    readPayLoad(ByteBuffer buff)
    Read the page payload from the buffer.
    void
    remove(int index)
    Remove the key and value (or child) at the given index.
    abstract int
    removeAllRecursive(long version)
    Remove all page data recursively.
    final int
    removePage(long version)
    Make accounting changes (chunk occupancy or "unsaved" RAM), related to this page removal.
    abstract void
    setChild(int index, Page<K,V> c)
    Replace the child page.
    void
    setComplete()
    Called when done with copying page.
    final void
    setKey(int index, K key)
    Replace the key at an index in this page.
    abstract V
    setValue(int index, V value)
    Replace the value at an index in this page.
    String
    toString()
     
    protected final int
    write(FileStore<?>.PageSerializationManager pageSerializationManager)
    Serializes this page into provided buffer, which represents content of the specified chunk to be persisted and updates the "position" of the page.
    protected abstract void
    writeChildren(WriteBuffer buff, boolean withCounts)
    Write page children to the buff.
    protected abstract void
    writeValues(WriteBuffer buff)
    Write values that the buffer contains to the buff.

    Methods inherited from class java.lang.Object

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

  • Field Details

    • map

      public final MVMap<K,V> map
      Map this page belongs to

    • pageNo

      public int pageNo
      Sequential 0-based number of the page within containing chunk.

  • Method Details

    • createNode

      public static <K, V> Page<K,V> createNode(MVMap<K,V> map, K[] keys, Page.PageReference<K,V>[] children, long totalCount, int memory)
      Create a new non-leaf page. The arrays are not cloned.
      Type Parameters:
      K - the key class
      V - the value class
      Parameters:
      map - the map
      keys - the keys
      children - the child page positions
      totalCount - the total number of keys
      memory - the memory used in bytes
      Returns:
      the page

    • getMapId

      public final int getMapId()
      Get the id of the page's owner map
      Returns:
      id

    • getKey

      public K getKey(int index)
      Get the key at the given index.
      Parameters:
      index - the index
      Returns:
      the key

    • getChildPage

      public abstract Page<K,V> getChildPage(int index)
      Get the child page at the given index.
      Parameters:
      index - the index
      Returns:
      the child page

    • getChildPagePos

      public abstract long getChildPagePos(int index)
      Get the position of the child.
      Parameters:
      index - the index
      Returns:
      the position

    • getValue

      public abstract V getValue(int index)
      Get the value at the given index.
      Parameters:
      index - the index
      Returns:
      the value

    • getKeyCount

      public final int getKeyCount()
      Get the number of keys in this page.
      Returns:
      the number of keys

    • isLeaf

      public final boolean isLeaf()
      Check whether this is a leaf page.
      Returns:
      true if it is a leaf

    • getNodeType

      public abstract int getNodeType()

    • getPos

      public final long getPos()
      Get the position of the page
      Returns:
      the position

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • dump

      protected void dump(StringBuilder buff)
      Dump debug data for this page.
      Parameters:
      buff - append buffer

    • copy

      public final Page<K,V> copy()
      Create a copy of this page.
      Returns:
      a mutable copy of this page

    • clone

      protected final Page<K,V> clone()
      Overrides:
      clone in class Object

    • getTotalCount

      public abstract long getTotalCount()
      Get the total number of key-value pairs, including child pages.
      Returns:
      the number of key-value pairs

    • setChild

      public abstract void setChild(int index, Page<K,V> c)
      Replace the child page.
      Parameters:
      index - the index
      c - the new child page

    • setKey

      public final void setKey(int index, K key)
      Replace the key at an index in this page.
      Parameters:
      index - the index
      key - the new key

    • setValue

      public abstract V setValue(int index, V value)
      Replace the value at an index in this page.
      Parameters:
      index - the index
      value - the new value
      Returns:
      the old value

    • insertLeaf

      public abstract void insertLeaf(int index, K key, V value)
      Insert a key-value pair into this leaf.
      Parameters:
      index - the index
      key - the key
      value - the value

    • insertNode

      public abstract void insertNode(int index, K key, Page<K,V> childPage)
      Insert a child page into this node.
      Parameters:
      index - the index
      key - the key
      childPage - the child page

    • remove

      public void remove(int index)
      Remove the key and value (or child) at the given index.
      Parameters:
      index - the index

    • readPayLoad

      protected abstract void readPayLoad(ByteBuffer buff)
      Read the page payload from the buffer.
      Parameters:
      buff - the buffer

    • isSaved

      public final boolean isSaved()

    • isRemoved

      public final boolean isRemoved()

    • write

      protected final int write(FileStore<?>.PageSerializationManager pageSerializationManager)
      Serializes this page into provided buffer, which represents content of the specified chunk to be persisted and updates the "position" of the page.
      Parameters:
      pageSerializationManager - which provides a target buffer and can be queried for various attributes related to serialization
      Returns:
      the position of the buffer, where serialized child page references (if any) begin

    • writeValues

      protected abstract void writeValues(WriteBuffer buff)
      Write values that the buffer contains to the buff.
      Parameters:
      buff - the target buffer

    • writeChildren

      protected abstract void writeChildren(WriteBuffer buff, boolean withCounts)
      Write page children to the buff.
      Parameters:
      buff - the target buffer
      withCounts - true if the descendant counts should be written

    • getRawChildPageCount

      public abstract int getRawChildPageCount()

    • isPersistent

      protected final boolean isPersistent()

    • getMemory

      public final int getMemory()

    • getDiskSpaceUsed

      public final long getDiskSpaceUsed(boolean approximate)
      Amount of used disk space in persistent case including child pages.
      Parameters:
      approximate - true to return quick approximation
      Returns:
      amount of used disk space in persistent case

    • calculateMemory

      protected int calculateMemory()
      Calculate estimated memory used in persistent case.
      Returns:
      memory in bytes

    • isComplete

      public boolean isComplete()

    • setComplete

      public void setComplete()
      Called when done with copying page.

    • removePage

      public final int removePage(long version)
      Make accounting changes (chunk occupancy or "unsaved" RAM), related to this page removal.
      Parameters:
      version - at which page was removed
      Returns:
      amount (negative), by which "unsaved memory" should be adjusted, if page is unsaved one, and 0 for page that was already saved, or in case of non-persistent map

    • getPrependCursorPos

      public abstract CursorPos<K,V> getPrependCursorPos(CursorPos<K,V> cursorPos)
      Extend path from a given CursorPos chain to "prepend point" in a B-tree, rooted at this Page.
      Parameters:
      cursorPos - presumably pointing to this Page (null if real root), to build upon
      Returns:
      new head of the CursorPos chain

    • getAppendCursorPos

      public abstract CursorPos<K,V> getAppendCursorPos(CursorPos<K,V> cursorPos)
      Extend path from a given CursorPos chain to "append point" in a B-tree, rooted at this Page.
      Parameters:
      cursorPos - presumably pointing to this Page (null if real root), to build upon
      Returns:
      new head of the CursorPos chain

    • removeAllRecursive

      public abstract int removeAllRecursive(long version)
      Remove all page data recursively.
      Parameters:
      version - at which page got removed
      Returns:
      adjustment for "unsaved memory" amount

    • createKeyStorage

      public final K[] createKeyStorage(int size)
      Create array for keys storage.
      Parameters:
      size - number of entries
      Returns:
      values array

    • createRefStorage

      public static <K, V> Page.PageReference<K,V>[] createRefStorage(int size)
      Create an array of page references.
      Type Parameters:
      K - the key class
      V - the value class
      Parameters:
      size - the number of entries
      Returns:
      the array