EclipseLink/Examples/JPA/QueryOptimization

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EclipseLink allows users the option to optimize their queries using batch and joined reading through the use of a query hint.

Via Annotations

@Entity
@Table(name="JPA_EMPLOYEE")
@NamedQuery(
  name="findEmployeeByPK",
  query="SELECT OBJECT(employee) FROM Employee employee WHERE employee.id = :id"),
  hints={
    @QueryHint(
      name=EclipseLinkQueryHints.BATCH, 
      value=EclipseLinkQueryHints.BATCH),
    @QueryHint(
      name=EclipseLinkQueryHints.FETCH, 
      value=EclipseLinkQueryHints.FETCH),
  }
)
public class Employee implements Serializable {
...

}

Via XML

<entity name="Employee" class="org.eclipse.testing.Employee" access="PROPERTY">
  ...
  <named-query name="findAllEmployeesByFirstName">
    <query>SELECT OBJECT(employee) FROM Employee employee WHERE employee.firstName = :firstname</query>
    <hint name="eclipselink.batch" value="eclipselink.batch">
    <hint name="eclipselink.join-fetch" value="eclipselink.join-fetch">
  </named-query>
  ...
</entity>