org.h2.util

Class CacheTQ

java.lang.Object

org.h2.util.CacheTQ

All Implemented Interfaces:

Cache

public class CacheTQ
extends java.lang.Object
implements Cache

An alternative cache implementation. This implementation uses two caches: a LRU cache and a FIFO cache. Entries are first kept in the FIFO cache, and if referenced again then marked in a hash set. If referenced again, they are moved to the LRU cache. Stream pages are never added to the LRU cache. It is supposed to be more or less scan resistant, and it doesn't cache large rows in the LRU cache.

Method Summary

Modifier and Type	Method and Description
void	clear() Clear the cache.
CacheObject	find(int pos) Get an element from the cache if it is available.
CacheObject	get(int pos) Get an element in the cache if it is available.
java.util.ArrayList<CacheObject>	getAllChanged() Get all objects in the cache that have been changed.
int	getMaxMemory() Get the maximum memory to be used.
int	getMemory() Get the used size in KB.
void	put(CacheObject r) Add an element to the cache.
boolean	remove(int pos) Remove an object from the cache.
void	setMaxMemory(int maxMemoryKb) Set the maximum memory to be used by this cache.
CacheObject	update(int pos, CacheObject record) Update an element in the cache.

Methods inherited from class java.lang.Object

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

Method Detail

clear

public void clear()

Description copied from interface: Cache

Clear the cache.

Specified by:

clear in interface Cache

find

public CacheObject find(int pos)

Description copied from interface: Cache

Get an element from the cache if it is available. This will not move the item to the front of the list.

Specified by:

find in interface Cache

Parameters:

pos - the unique key of the element

Returns:

the element or null

get

public CacheObject get(int pos)

Description copied from interface: Cache

Get an element in the cache if it is available. This will move the item to the front of the list.

Specified by:

get in interface Cache

Parameters:

pos - the unique key of the element

Returns:

the element or null

getAllChanged

public java.util.ArrayList<CacheObject> getAllChanged()

Description copied from interface: Cache

Get all objects in the cache that have been changed.

Specified by:

getAllChanged in interface Cache

Returns:

the list of objects

getMaxMemory

public int getMaxMemory()

Description copied from interface: Cache

Get the maximum memory to be used.

Specified by:

getMaxMemory in interface Cache

Returns:

the maximum size in KB

getMemory

public int getMemory()

Description copied from interface: Cache

Get the used size in KB.

Specified by:

getMemory in interface Cache

Returns:

the current size in KB

put

public void put(CacheObject r)

Description copied from interface: Cache

Add an element to the cache. Other items may fall out of the cache because of this. It is not allowed to add the same record twice.

Specified by:

put in interface Cache

Parameters:

r - the object

remove

public boolean remove(int pos)

Description copied from interface: Cache

Remove an object from the cache.

Specified by:

remove in interface Cache

Parameters:

pos - the unique key of the element

Returns:

true if the key was in the cache

setMaxMemory

public void setMaxMemory(int maxMemoryKb)

Description copied from interface: Cache

Set the maximum memory to be used by this cache.

Specified by:

setMaxMemory in interface Cache

Parameters:

maxMemoryKb - the maximum size in KB

update

public CacheObject update(int pos,
                          CacheObject record)

Description copied from interface: Cache

Update an element in the cache. This will move the item to the front of the list.

Specified by:

update in interface Cache

Parameters:

pos - the unique key of the element

record - the element

Returns:

the element