Hi,
I'm using JPA 2.0, Hibernate 3.5.0-Beta4, MySQL 5.1 on Glassfish v3.
I want to limit the polymorphic query results using JPA 2.0 syntax (TYPE) :

SELECT e FROM Employee e WHERE TYPE(e) IN (FullTime, Executive)

but it seems that Hibernate 3.5.0-Beta4 doesn't support this syntax because in the generated sql query the 'type' keyword remains unmapped and MySQL throws an Exception:

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(type(employee0_.id) in (5))' at line 1

So I tried with Criteria API:

CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
CriteriaQuery<Employee> criteria = criteriaBuilder.createQuery(Employee.class);
Root<Employee> employee= criteria.from(Employee.class);
criteria.where(employee.type().in(FullTime.class,Executive.class));

But I received an Exception:

Caused by: java.lang.IllegalArgumentException: Unexpected call on EntityTypeExpression#render
at org.hibernate.ejb.criteria.expression.PathTypeExpression.render(PathTypeExpression.java:48)
at org.hibernate.ejb.criteria.predicate.InPredicate.render(InPredicate.java:164)
at org.hibernate.ejb.criteria.QueryStructure.render(QueryStructure.java:258)
at org.hibernate.ejb.criteria.CriteriaQueryImpl.render(CriteriaQueryImpl.java:340)
at org.hibernate.ejb.criteria.CriteriaQueryCompiler.compile(CriteriaQueryCompiler.java:150)
at org.hibernate.ejb.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:416)
at com.sun.enterprise.container.common.impl.EntityManagerWrapper.createQuery(EntityManagerWrapper.java:489)

So I opened the PathTypeExpression class and in the render method I saw :

public String render(CriteriaQueryCompiler.RenderingContext renderingContext) {
// todo : is it valid for this to get rendered into the query itself?
throw new IllegalArgumentException( "Unexpected call on EntityTypeExpression#render" );
}

Then I switched to use Hibernate custom query syntax (class) :

SELECT e FROM Employee e WHERE (e.class) IN (FullTime, Executive)

Ok this works fine.
But when I add a join with another entity (Department) that has the same TABLE_PER_CLASS inheritance strategy of entity Employee, I have a new problem:

SELECT e FROM Employee e JOIN e.departments d WHERE d.code = 'D1' and (e.class) IN (FullTime, Executive)

GRAVE: Column 'clazz_' in where clause is ambiguous
Caused by: javax.persistence.PersistenceException: org.hibernate.exception.ConstraintViolationException: could not execute query

How can I restrict the polymorphic query results in Hibernate using JPA 2.0 standard syntax?

Thanks in advance
Domenico