Entity cache is provided by EclipseLink ORM framework. It stores recently read or written entity instance in memory, which minimizes database access and improves the application performance.

Entity cache is used only when you retrieve entities by ID, so queries by other attributes still run on the database. However, these queries can be simpler and faster if related entities are in cache. For example, if you query for Orders together with related Customers and do not use cache, the SQL query will contain a JOIN for customers table. If Customer entities are cached, the SQL query will select only orders, and related customers will be retrieved from the cache.

In order to turn on entity cache, set the following properties in the app.properties file of your core module:

The fact of whether an entity is cached affects the fetch mode chosen by the platform for loading entity graphs. If a reference attribute is a cacheable entity, the fetch mode is always UNDEFINED, which allows ORM to retrieve the reference from the cache instead of executing queries with JOINs or separate batch queries.

The platform provides entity cache coordination in middleware cluster. When a cached entity is updated or deleted on one cluster node, the same cached instance on other nodes (if any) will be invalidated, so the next operation with this instance will read a fresh state from the database.

Query cache stores identifiers of entity instances returned by JPQL queries, so it naturally complements the entity cache.

For example, if entity cache is enabled for an entity (say, sales$Customer), and you execute the query select c from sales$Customer c where c.grade = :grade for the first time, the following happens:

When you execute the same query with the same parameters the second time, the platform finds the query in the query cache and loads entity instances from the entity cache by identifiers. No database operations are needed.

Queries are not cached by default. You can specify that a query should be cached on different layers of the application:

Query cache is invalidated automatically when ORM performs creation, update or deletion of instances of the corresponding entities. The invalidation works across the middleware cluster.

The app-core.cuba:type=QueryCacheSupport JMX-bean can be used to monitor the cache state and to evict cached queries manually. For example, if you have modified an instance of the sales$Customer entity directly in the database, you should evict all cached queries for this entity using the evict() operation with sales$Customer argument.

The following application properties affect the query cache: