org.h2.util
Class CacheTQ

java.lang.Object
  extended by 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
 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