org.h2.dev.store.btree
Class Page

java.lang.Object
  org.h2.dev.store.btree.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)

Method Summary

int	binarySearch(java.lang.Object key) Search the key in this page using a binary search.
Page	copyOnWrite(long writeVersion) Create a copy of this page, if the write version is higher than the current version.
static Page	create(MVMap<?,?> map, long version, int keyCount, java.lang.Object[] keys, java.lang.Object[] values, long[] children, Page[] childrenPages, long[] counts, long totalCount, int sharedFlags) Create a new page.
static Page	createEmpty(MVMap<?,?> map, long version) Create a new, empty page.
Page	getChildPage(int index) Get the child page at the given index.
java.lang.Object	getKey(int index) Get the key at the given index.
int	getKeyCount() Get the number of keys in this page.
long	getPos() Get the position of the page
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.
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 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	setChild(int index, Page c) Replace the child page.
void	setKey(int index, java.lang.Object key) Replace the key.
java.lang.Object	setValue(int index, java.lang.Object value) Replace the value.
Page	split(int at) Split the page.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Method Detail

createEmpty

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

Create a new, empty page.

Parameters:

map - the map

version - the version

Returns:

the new page

create

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

Create a new page. The arrays are not cloned.

Parameters:

map - the map

version - the version

keyCount - the number of keys

keys - the keys

values - the values

children - the children

childrenPages - the children pages

counts - the children counts

totalCount - the total number of keys

sharedFlags - which arrays are shared

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

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

copyOnWrite

public Page copyOnWrite(long writeVersion)

Create a copy of this page, if the write version is higher than the current version.

Parameters:

writeVersion - the write version

Returns:

a page with the given write 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

split

public Page split(int at)

Split the page. This modifies the current page.

Parameters:

at - the split index

Returns:

the page with the entries after the split index

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.

Parameters:

index - the index

key - the new key

setValue

public java.lang.Object setValue(int index,
                                 java.lang.Object value)

Replace the value.

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 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