t_RelationalMapping_AttributeMappings_AttributeMapping_PersistenceMapping

PersistenceMapping

A persistence mapping specifies how instances are persisted in a given data source. The type of the specified data source determines the mapping structure.

Properties

caching

Caching mode: instance - individual instances are cached, class - all instances are cached.

Instance mode - Queries that are guaranteed to return <= 1 instance are cached if they return 1 instance. A change to a given instance invalidates the cache for that particular instance.

Class mode - All instances of the class are pre-read and cached. Queries are evaluated against this cache. If the query is an instance query (see above) and the cached instance count is > 64, then instance caching is used as well and the query is evaluated against the persistence store on cache miss. A change to an instance of the class or subclass invalidates the whole cache for the class.

Heterogeneous joins (which are used for joining cached instances to a query) work with both types of caching. Caching is turned off for query subtrees that would require heterogeneous joins in the where clause if caching were used.

Valid values based on“string”.
instance
class

dataSource : string

Persistent datasource, in which the instances of this class are stored.

The type of the selected datasource will dictate what sort of mapping is presented to the developer in NexJ Studio.

Content

Choice of:
- t_PersistenceMapping_RelationalMapping [1..1]
- t_PersistenceMapping_FileStorageMapping [1..1]
- t_PersistenceMapping_ServiceMapping [1..1]
- t_PersistenceMapping_XMLMapping [1..1]
- t_PersistenceMapping_CustomMapping [1..1]
- t_PersistenceMapping_CompositeMapping [1..1]

Parents

t_RelationalMapping_AttributeMappings_AttributeMapping - Class attribute's mapping to a relational database column

Parent topic: t_RelationalMapping_AttributeMappings_AttributeMapping