org.h2.mvstore

Class Page

java.lang.Object

org.h2.mvstore.Page

public class Page
extends java.lang.Object

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.PageChildren Contains information about which other pages are referenced (directly or indirectly) by the given page.
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
static java.lang.Object[]	EMPTY_OBJECT_ARRAY An empty object array.

Method Summary

Modifier and Type	Method and Description
int	binarySearch(java.lang.Object key) Search the key in this page using a binary search.
Page	copy(long version) Create a copy of this page.
static Page	create(MVMap<?,?> map, long version, java.lang.Object[] keys, java.lang.Object[] values, Page.PageReference[] children, long totalCount, int memory) Create a new page.
static Page	create(MVMap<?,?> map, long version, Page source) Create a copy of a page.
boolean	equals(java.lang.Object other)
Page	getChildPage(int index) Get the child page at the given index.
long	getChildPagePos(int index) Get the position of the child.
java.lang.Object	getKey(int index) Get the key at the given index.
int	getKeyCount() Get the number of keys in this page.
int	getMemory()
long	getPos() Get the position of the page
int	getRawChildPageCount()
long	getTotalCount() Get the total number of key-value pairs, including child pages.
java.lang.Object	getValue(int index) Get the value at the given index.
int	hashCode()
void	insertLeaf(int index, java.lang.Object key, java.lang.Object value) Insert a key-value pair into this leaf.
void	insertNode(int index, java.lang.Object key, Page childPage) Insert a child page into this node.
boolean	isLeaf() Check whether this is a leaf page.
void	remove(int index) Remove the key and value (or child) at the given index.
void	removePage() Remove the page.
void	setChild(int index, Page c) Replace the child page.
void	setKey(int index, java.lang.Object key) Replace the key at an index in this page.
java.lang.Object	setValue(int index, java.lang.Object value) Replace the value at an index in this page.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

EMPTY_OBJECT_ARRAY

public static final java.lang.Object[] EMPTY_OBJECT_ARRAY

An empty object array.

Method Detail

create

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

Create a new page. The arrays are not cloned.

Parameters:

map - the map

version - the version

keys - the keys

values - the values

children - the child page positions

totalCount - the total number of keys

memory - the memory used in bytes

Returns:

the page

create

public static Page create(MVMap<?,?> map,
                          long version,
                          Page source)

Create a copy of a page.

Parameters:

map - the map

version - the version

source - the source page

Returns:

the page

getKey

public java.lang.Object getKey(int index)

Get the key at the given index.

Parameters:

index - the index

Returns:

the key

getChildPage

public Page getChildPage(int index)

Get the child page at the given index.

Parameters:

index - the index

Returns:

the child page

getChildPagePos

public long getChildPagePos(int index)

Get the position of the child.

Parameters:

index - the index

Returns:

the position

getValue

public java.lang.Object getValue(int index)

Get the value at the given index.

Parameters:

index - the index

Returns:

the value

getKeyCount

public int getKeyCount()

Get the number of keys in this page.

Returns:

the number of keys

isLeaf

public boolean isLeaf()

Check whether this is a leaf page.

Returns:

true if it is a leaf

getPos

public long getPos()

Get the position of the page

Returns:

the position

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

copy

public Page copy(long version)

Create a copy of this page.

Parameters:

version - the new version

Returns:

a page with the given version

binarySearch

public int binarySearch(java.lang.Object key)

Search the key in this page using a binary search. Instead of always starting the search in the middle, the last found index is cached.

If the key was found, the returned value is the index in the key array. If not found, the returned value is negative, where -1 means the provided key is smaller than any keys in this page. See also Arrays.binarySearch.

Parameters:

key - the key

Returns:

the value or null

getTotalCount

public long getTotalCount()

Get the total number of key-value pairs, including child pages.

Returns:

the number of key-value pairs

setChild

public void setChild(int index,
                     Page c)

Replace the child page.

Parameters:

index - the index

c - the new child page

setKey

public 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 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 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 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

getRawChildPageCount

public int getRawChildPageCount()

equals

public boolean equals(java.lang.Object other)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

getMemory

public int getMemory()

removePage

public void removePage()

Remove the page.