org.h2.mvstore

Class Page

java.lang.Object

org.h2.mvstore.Page

All Implemented Interfaces:

java.lang.Cloneable

public abstract class Page
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.

File format: page length (including length): int check value: short map id: varInt number of keys: varInt type: byte (0: leaf, 1: node; +2: compressed) compressed: bytes saved (varInt) keys leaf: values (one for each key) node: children (1 more than keys)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Page.PageReference A pointer to a page, either in-memory or using a page position.

Field Summary

Fields

Modifier and Type	Field and Description
MVMap<?,?>	map Map this page belongs to

Method Summary

Methods

Modifier and Type	Method and Description
protected int	calculateMemory() Calculate estimated memory used in persistent case.
protected Page	clone()
Page	copy() Create a copy of this page.
static Page	createNode(MVMap<?,?> map, java.lang.Object[] keys, Page.PageReference[] children, long totalCount, int memory) Create a new non-leaf page.
protected void	dump(java.lang.StringBuilder buff) Dump debug data for this page.
boolean	equals(java.lang.Object other)
abstract CursorPos	getAppendCursorPos(CursorPos cursorPos) Extend path from a given CursorPos chain to "append point" in a B-tree, rooted at this Page.
abstract Page	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.
java.lang.Object	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	getPrependCursorPos(CursorPos 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 java.lang.Object	getValue(int index) Get the value at the given index.
int	hashCode()
abstract void	insertLeaf(int index, java.lang.Object key, java.lang.Object value) Insert a key-value pair into this leaf.
abstract void	insertNode(int index, java.lang.Object key, Page 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 c) Replace the child page.
void	setComplete() Called when done with copying page.
void	setKey(int index, java.lang.Object key) Replace the key at an index in this page.
abstract java.lang.Object	setValue(int index, java.lang.Object value) Replace the value at an index in this page.
java.lang.String	toString()
protected int	write(Chunk chunk, WriteBuffer buff) Store the page and update the position.
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

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

Field Detail

map

public final MVMap<?,?> map

Map this page belongs to

Method Detail

createNode

public static Page createNode(MVMap<?,?> map,
              java.lang.Object[] keys,
              Page.PageReference[] children,
              long totalCount,
              int memory)

Create a new non-leaf page. The arrays are not cloned.

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 java.lang.Object getKey(int index)

Get the key at the given index.

Parameters:

index - the index

Returns:

the key

getChildPage

public abstract Page 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 java.lang.Object 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 copy()

Create a copy of this page.

Returns:

a mutable copy of this page

clone

protected final Page 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 c)

Replace the child page.

Parameters:

index - the index

c - the new child page

setKey

public final void setKey(int index,
          java.lang.Object key)

Replace the key at an index in this page.

Parameters:

index - the index

key - the new key

setValue

public abstract java.lang.Object setValue(int index,
                        java.lang.Object 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,
              java.lang.Object key,
              java.lang.Object 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,
              java.lang.Object key,
              Page 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(Chunk chunk,
        WriteBuffer buff)

Store the page and update the position.

Parameters:

chunk - the chunk

buff - the target buffer

Returns:

the position of the buffer just after the type

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()

equals

public final boolean equals(java.lang.Object other)

Overrides:

equals in class java.lang.Object

hashCode

public final int hashCode()

Overrides:

hashCode in class java.lang.Object

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 getPrependCursorPos(CursorPos 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 getAppendCursorPos(CursorPos 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