Page

java.lang.Object
- org.h2.mvstore.Page<K,V>

All Implemented Interfaces:

java.lang.Cloneable
```
public abstract class Page<K,V>
extends java.lang.Object
implements java.lang.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 and Description

static class Page.PageReference<K,V>
A pointer to a page, either in-memory or using a page position.

Nested Classes
Modifier and Type	Class and Description
`static 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 and Description

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

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

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

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`protected int`	`calculateMemory()` Calculate estimated memory used in persistent case.
`protected Page<K,V>`	`clone()`
`Page<K,V>`	`copy()` Create a copy of this page.
`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(java.lang.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.
`long`	`getDiskSpaceUsed()` Amount of used disk space in persistent case including child pages.
`K`	`getKey(int index)` Get the key at the given index.
`int`	`getKeyCount()` Get the number of keys in this page.
`int`	`getMapId()` Get the id of the page's owner map
`int`	`getMemory()`
`abstract int`	`getNodeType()`
`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()`
`boolean`	`isLeaf()` Check whether this is a leaf page.
`protected boolean`	`isPersistent()`
`boolean`	`isRemoved()`
`boolean`	`isSaved()`
`protected abstract void`	`readPayLoad(java.nio.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.
`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.
`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.
`java.lang.String`	`toString()`
`protected 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 Detail
  - 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 Detail
  - 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 java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object
  - dump
```
protected void dump(java.lang.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 java.lang.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(java.nio.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 long getDiskSpaceUsed()
```
    Amount of used disk space in persistent case including child pages.
    
    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

Class Page<K,V>

Nested Class Summary

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

map

pageNo

Method Detail

createNode

getMapId

getKey

getChildPage

getChildPagePos

getValue

getKeyCount

isLeaf

getNodeType

getPos

toString

dump

copy

clone

getTotalCount

setChild

setKey

setValue

insertLeaf

insertNode

remove

readPayLoad

isSaved

isRemoved

write

writeValues

writeChildren

getRawChildPageCount

isPersistent

getMemory

getDiskSpaceUsed

calculateMemory

isComplete

setComplete

removePage

getPrependCursorPos

getAppendCursorPos

removeAllRecursive

createKeyStorage

createRefStorage