EclipseLink/UserGuide/JPA/Basic JPA Development/Caching/Query Cache

EclipseLink JPA

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Key API

• QueryHints

Native API

• QueryResultsCachePolicy

Query Results Cache

By default in EclipseLink all queries that are not by Id, or not by cache indexed fields, will access the database. The resulting rows will still be resolved with the cache, and further queries for relationship will be avoided if the object is cached, but the original query will always access the database. EclipseLink does have options for querying the cache, but these cannot be used by default, as they can not assume that all of the objects are in the cache.

Query results cache annotation example

...
@Entity
@CacheIndex(columnNames={"F_NAME", "L_NAME"}, updateable=true)
public class Employee {
  @Id
  private long id;
  @CacheIndex
  private String ssn;
  @Column(name="F_NAME")
  private String firstName;
  @Column(name="L_NAME")
  private String lastName;
}

Query results cache XML example

<?xml version="1.0"?>
<entity-mappings
	xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/orm"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.eclipse.org/eclipselink/xsds/persistence/orm http://www.eclipse.org/eclipselink/xsds/eclipselink_orm_2_4.xsd"
	version="2.4">
    <entity name="Employee" class="org.acme.Employee" access="FIELD">
        <cache-index updateable="true">
            <column-name>F_NAME</column-name>
            <column-name>L_NAME</column-name>
        </cache-index>
        <attributes>
            <id name="id"/>
            <basic name="ssn">
                <cache-index/>
            </basic>
            <basic name="firstName">
                <column name="F_NAME"/>
            </basic>
            <basic name="lastName">
                <column name="L_NAME"/>
            </basic>
        </attributes>
    </entity>
</entity-mappings>

Query results cache query example

Query query = em.createNamedQuery("findAllEmployeesInCity");
query.setParameter("city", "Ottawa");
List<Employee> employees = query.getResultList();

Version: 2.4 DRAFT
Other versions...

Cache Indexes	Caching	Clustering and Cache Coordination
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