org.h2.store

Class PageFreeList

java.lang.Object

org.h2.util.CacheObject

org.h2.store.Page

org.h2.store.PageFreeList

All Implemented Interfaces:

java.lang.Comparable<CacheObject>

public class PageFreeList
extends Page

The list of free pages of a page store. The format of a free list trunk page is:

• page type: byte (0)
• checksum: short (1-2)
• data (3-)

Field Summary

Fields inherited from class org.h2.store.Page

changeCount, FLAG_LAST, TYPE_BTREE_LEAF, TYPE_BTREE_NODE, TYPE_DATA_LEAF, TYPE_DATA_NODE, TYPE_DATA_OVERFLOW, TYPE_EMPTY, TYPE_FREE_LIST, TYPE_STREAM_DATA, TYPE_STREAM_TRUNK

Fields inherited from class org.h2.util.CacheObject

cacheChained, cacheNext, cachePrevious

Method Summary

Modifier and Type	Method and Description
boolean	canMove() If this page can be moved.
boolean	canRemove() Check if the object can be removed from the cache.
int	getMemory() Get the estimated memory size.
static int	getPagesAddressed(int pageSize) Get the number of pages that can fit in a free list.
void	moveTo(Session session, int newPos) Copy the data to a new location, change the parent to point to the new location, and free up the current page.
java.lang.String	toString()
void	write() Write the page.

Methods inherited from class org.h2.store.Page

add, insert, insert, insert, remove, remove, remove

Methods inherited from class org.h2.util.CacheObject

compareTo, getPos, isChanged, isStream, setChanged, setPos

Methods inherited from class java.lang.Object

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

Method Detail

write

public void write()

Description copied from class: Page

Write the page.

Specified by:

write in class Page

getPagesAddressed

public static int getPagesAddressed(int pageSize)

Get the number of pages that can fit in a free list.

Parameters:

pageSize - the page size

Returns:

the number of pages

getMemory

public int getMemory()

Get the estimated memory size.

Specified by:

getMemory in class CacheObject

Returns:

number of double words (4 bytes)

moveTo

public void moveTo(Session session,
                   int newPos)

Description copied from class: Page

Copy the data to a new location, change the parent to point to the new location, and free up the current page.

Specified by:

moveTo in class Page

Parameters:

session - the session

newPos - the new position

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

canRemove

public boolean canRemove()

Description copied from class: CacheObject

Check if the object can be removed from the cache. For example pinned objects can not be removed.

Specified by:

canRemove in class CacheObject

Returns:

true if it can be removed

canMove

public boolean canMove()

Description copied from class: Page

If this page can be moved. Transaction log and free-list pages can not.

Overrides:

canMove in class Page

Returns:

true if moving is allowed