kodo.datacache
Interface QueryCache

All Superinterfaces:

com.solarmetric.util.Closeable

All Known Implementing Classes:

AbstractQueryCache

public interface QueryCache

extends com.solarmetric.util.Closeable

Interface that must be implemented by any level 2 query cache used by Kodo. These methods should be synchronized. Most query cache implementations will probably implement Configurable to receive a handle to the system configuration on construction.

Since:

2.5

Method Summary

void	addExpirationListener(ExpirationListener listen) Add a new expiration event listener to this cache.
void	classesChanged(Collection classes) Tells the cache that all the classes in the classes set have been changed.
void	clear() Remove all data from this cache.
void	close() Free the resources used by this cache.
QueryResult	get(QueryKey qk) Return a list of oids for the given query key.
boolean	pin(QueryKey qk) Pin the value stored under qk into the cache.
QueryResult	put(QueryKey qk, QueryResult oids) Set the list of OIDs for the given query key.
QueryResult	remove(QueryKey qk) Remove the value stored under the given query key.
boolean	removeExpirationListener(ExpirationListener listen) Remove an expiration event listener from this cache.
boolean	unpin(QueryKey qk) Unpin the value stored under key into the cache.

Method Detail

classesChanged

public void classesChanged(Collection classes)

Tells the cache that all the classes in the classes set have been changed. This could mean that items have been updated, deleted, or added. This limits the QueryCache to only be able to invalidate cached queries -- because the cache is not notified of actual changes, it cannot recompute query results.

After this method is invoked, all cached results that correspond to queries that use one of the classes in classes will be dropped.

Parameters:

classes - a set of Class objects that correspond to instances that have changed

get

public QueryResult get(QueryKey qk)

Return a list of oids for the given query key. This is an unmodifiable list.

Returns:

The query results matching the given key, or null if none

put

public QueryResult put(QueryKey qk,
                       QueryResult oids)

Set the list of OIDs for the given query key. A reference to the given list will be stored in the query cache, so the list should not be modified after invoking this method.

Returns:

The previously cached value, or null if the key was not previously cached. See Map.put(java.lang.Object, java.lang.Object) for more information.

remove

public QueryResult remove(QueryKey qk)

Remove the value stored under the given query key.

This method is typically not invoked directly from outside the QueryCache class. Instead, the cache should be updated by invoking #notifyChangedClasses, which will result in all queries that may be invalid being dropped.

Returns:

The previously cached value, or null if the key was not previously cached. See Map.remove(java.lang.Object) for more information.

clear

public void clear()

Remove all data from this cache.

pin

public boolean pin(QueryKey qk)

Pin the value stored under qk into the cache. This method guarantees that qk's value will not be expired if the cache exceeds its capacity. It causes this data to be ignored when determining whether or not the cache is full, effectively increasing the total amount of data stored in the cache. This method does not affect the behavior of remove(kodo.datacache.QueryKey) or #notifyChangedClasses.

Returns:

true if key's value was pinned into the cache; false if the key is not in the cache.

unpin

public boolean unpin(QueryKey qk)

Unpin the value stored under key into the cache. This method reverses a previous invocation of pin(kodo.datacache.QueryKey). This method does not remove anything from the cache; it merely makes key's value a candidate for flushing from the cache.

Returns:

true if key's value was unpinned from the cache; false if the key is not in the cache.

addExpirationListener

public void addExpirationListener(ExpirationListener listen)

Add a new expiration event listener to this cache.

Since:

3.3

removeExpirationListener

public boolean removeExpirationListener(ExpirationListener listen)

Remove an expiration event listener from this cache.

Since:

3.3

close

public void close()

Free the resources used by this cache.

Specified by:

close in interface com.solarmetric.util.Closeable