ch.agent.crnickl.impl

Interface DatabaseCache

All Known Implementing Classes:

DatabaseCacheImpl

public interface DatabaseCache

A DatabaseCache is used to provide fast access to frequently used chronicles and their schemas. Schema objects are expensive to load from the database. Using this cache greatly improves performance under two easy assumptions:

1. a large database (millions of chronicles, hundreds of millions of values) requires only a small number of schemas (hundreds), and
2. schemas a very rarely modified.

When a chronicle is stored in the cache, its parent chronicle, its parent's parent, and so on, are also stored. Its schema and all the properties used in the schema are stored. Naturally, all equal objects are stored only once.

Author:

Jean-Paul Vetterli

Method Summary

Modifier and Type	Method and Description
void	clear() Clear the cache.
void	clear(Chronicle chronicle) Remove a chronicle from the cache if present.
void	clear(Property<?> property) Remove a property from the cache if present.
void	clear(Schema schema) Remove a schema from the cache if present.
void	clear(ValueType<?> valueType) Remove a value type from the cache if present.
ChronicleImpl	lookUpChronicle(String name) Look up a chronicle in the cache by name.
ChronicleImpl	lookUpChronicle(Surrogate surrogate) Look up a chronicle in the cache.
Property<?>	lookUpProperty(String name) Look up a property in the cache by name.
int	size() Return the number of chronicles currently in the cache.
ChronicleImpl	store(ChronicleImpl chronicle) Store a chronicle in the cache and return a copy.

Method Detail

lookUpChronicle

ChronicleImpl lookUpChronicle(Surrogate surrogate)

Look up a chronicle in the cache. Return null if not found.

Parameters:

surrogate - a chronicle surrogate

Returns:

a chronicle or null

lookUpChronicle

ChronicleImpl lookUpChronicle(String name)

Look up a chronicle in the cache by name. Return null if not found.

Parameters:

name - a string

Returns:

a chronicle or null

lookUpProperty

Property<?> lookUpProperty(String name)
                    throws T2DBException

Look up a property in the cache by name. If not in the cache get it from the database. Throw an exception if not found. This method is meant for accessing "built-in" properties

Parameters:

name - a string

Returns:

a property

Throws:

T2DBException

store

ChronicleImpl store(ChronicleImpl chronicle)
             throws T2DBException

Store a chronicle in the cache and return a copy. Return null if the chronicle was not kept in the cache for some reason.

Parameters:

chronicle - a chronicle

Returns:

a chronicle or null

Throws:

T2DBException

size

int size()

Return the number of chronicles currently in the cache.

Returns:

the number of chronicles in the cache

clear

void clear(Chronicle chronicle)

Remove a chronicle from the cache if present. This method must be called before renaming or deleting a chronicle.

Parameters:

chronicle - a chronicle

clear

void clear(Schema schema)

Remove a schema from the cache if present. This method must be called before renaming or deleting a schema.

Parameters:

schema - a schema

clear

void clear(Property<?> property)

Remove a property from the cache if present. This method must be called before renaming or deleting a property.

Parameters:

property - a property

clear

void clear(ValueType<?> valueType)

Remove a value type from the cache if present. This method must be called before modifying or deleting a value type.

Parameters:

valueType - a valueType

clear

void clear()

Clear the cache.