When you have an inheritance hierarchy with "joined" inheritance type and query something from a subclass, superclass is always joined in the query even though it is not needed. Example:
{code:java}
@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class A {
@Id
@GeneratedValue
private Long id;
private String valA;
// getters setters here
}
{code}
{code:java}
@Entity
public class SubA extends A {
private String valSubA;
// getters setters here
}
{code}
JPQL query:
{code :hql }
select suba.valSubA from SubA suba
{code}
Translated SQL query:
{code:sql}
select suba0_.valSubA as col_0_0_ from SubA suba0_ inner join A suba0_1_ on suba0_.id=suba0_1_.id
{code}
Super class table join is useless in the SQL query. It could be optimized.
I discussed that on [Hibernate forum|https://discourse.hibernate.org/t/how-to-omit-joining-of-superclass-in-jpa-when-im-querying-subclass-only/1310] |
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