PostgreSQL identity in JPA single table hierarchy

Question

I'm seeing strange behaviour when using PostgreSQL in a Hibernate/JPA environment with a single table inheritance hierarchy.

Firstly my environment:

• PostgreSQL 8.3
• Spring 2.5.6SEC01
• Hibernate-entitymanager 3.4.0.GA (installed from Glassfish update tool)
• Hibernate-distribution 3.3.1.GA (installed from Glassfish update tool)
• Glassfish V2
• Mac OS X 10.5.x

I'm having an issue when using a GenerationType of IDENTITY with a single table inheritance hierarchy.

Here are my two entities:

Parent.java

@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="generation", discriminatorType=DiscriminatorType.STRING)
@DiscriminatorValue("Parent")
public class Parent implements Serializable {
    private static final long serialVersionUID = 1L;

    private Long id;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }
}

Child.java

@Entity
@DiscriminatorValue("Child")
public class Child extends Parent {
    private String babyName;

    /**
     * @return the babyName
     */
    public String getBabyName() {
        return babyName;
    }

    /**
     * @param babyName the babyName to set
     */
    public void setBabyName(String babyName) {
        this.babyName = babyName;
    }
}

DDL

create table Parent (generation varchar(31) not null
                    ,id  bigserial not null
                    ,babyName varchar(255)
                    ,primary key (id)
                    );

If I try to insert a new Parent I get an error:

org.postgresql.util.PSQLException: Bad value for type long : Parent

I turned up the logging to TRACE and this is the output:

TRACE TransactionSynchronizationManager - Bound value [org.springframework.orm.jpa.EntityManagerHolder@485e0366] for key [com.sun.enterprise.util.EntityManagerFactoryWrapper@a6e312b] to thread [httpSSLWorkerThread-8080-0]
Hibernate: insert into Parent (generation) values ('Parent')
SQL Error: 0, SQLState: 22003
Bad value for type long : Parent
TRACE TransactionInterceptor - Completing transaction for [com.xxx.yyy.service.MoveService.saveHuman] after exception: javax.persistence.PersistenceException: org.hibernate.exception.DataException: could not insert: [com.xxx.yyy.temp.Parent]
TRACE RuleBasedTransactionAttribute - Applying rules to determine whether transaction should rollback on javax.persistence.PersistenceException: org.hibernate.exception.DataException: could not insert: [com.xxx.yyy.temp.Parent]

If I change the discriminator value to be something that parses as a long e.g. 123 the insert succeeds. However Hibernate seems to think this discriminator value is the id. So the following code:

Parent p = new Parent();
service.saveHuman(p);

add(new Label("p", "p id is" + p.getId()));

Shows the id as 123 rather than the primary key value which is 1.

If I change the generation type to AUTO a single sequence is created and the insert seems to work ok. If I change it to SEQUENCE and declare the sequence with a class-level annotation again it works. However according to the documentation I have read PostgreSQL supports both generation types.

I also tried the exact same code and switched out the database with MySQL 5.0.51b. This seems to function fine.

So is this a bug in my code, the dialect, Hibernate, or the PostgreSQL JDBC driver? Any ideas how I can narrow down the problem? Anyone able to re-produce this issue as I have tried to search and haven't seen this exact problem yet.

Note: I've also asked the question on the Hibernate Forums. Naturally I will feedback any responses to both sites.

Answer 1

I'm just "porting" this solution from the comments above... use version 8.3 of the PostgreSQL JDBC driver :-).