[hibernate-issues] [Hibernate-JIRA] Created: (JPA-6) @ManyToOne target using Single Table inheritance type

[Michal Jastak (JIRA)]

@ManyToOne target using Single Table inheritance type
-----------------------------------------------------

                 Key: JPA-6
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/JPA-6
             Project: Java Persistence API
          Issue Type: Bug
    Affects Versions: 1.0.0
         Environment: hibernate annotations 3.4.0 GA, hibernate entity manager 3.4.0 GA, spring framework 3.0.4, database: Mysql (tested on Oracle as well)
            Reporter: Michal Jastak


It looks like the wrong SQL is generated when you use the @ManyToOne which target entity is using Single Table inheritance type, see the example below:

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "D_TYPE")
@Table(name = "DICTIONARIES")
public abstract class DictionaryItem implements Serializable {

    private String description;
    private Long id;

    @Basic
    public String getDescription() {
        return description;
    }

    @Id
    public Long getId() {
        return id;
    }
...
}

@Entity
@DiscriminatorValue("MaterialType")
public class MaterialType extends DictionaryItem {

    // Empty by design ...
}

@Entity
@javax.persistence.Table(name = "TABLES")
public class Table implements Serializable {

    private Long id;
    private MaterialType legsMaterial;

    @Id
    public Long getId() {
        return id;
    }

    @ManyToOne
    @JoinColumn(name = "LEG_MATERIAL")
    public MaterialType getLegsMaterial() {
        return legsMaterial;
    }
...
}

@Repository("persistence.TableDAO")
public class DefaultTableDAO implements TableDAO {

    @PersistenceContext
    private EntityManager entityManager;

    public Table get(Long id) {
        return entityManager.find(Table.class, id);
    }

...
}

DB tables:

CREATE TABLE DICTIONARIES (
    ID            NUMERIC NOT NULL,
    D_TYPE        VARCHAR(32),    
    DESCRIPTION   VARCHAR(64),
    CONSTRAINT DICTIONARIES_PK PRIMARY KEY (ID, D_TYPE)
);

INSERT INTO DICTIONARIES(ID, D_TYPE, DESCRIPTION) VALUES (1, 'MaterialType', 'Wood');
INSERT INTO DICTIONARIES(ID, D_TYPE, DESCRIPTION) VALUES (2, 'MaterialType', 'Glass');
INSERT INTO DICTIONARIES(ID, D_TYPE, DESCRIPTION) VALUES (1, 'SomeOtherType', 'SOT1');
INSERT INTO DICTIONARIES(ID, D_TYPE, DESCRIPTION) VALUES (2, 'SomeOtherType', 'SOT2');

CREATE TABLE TABLES (
    ID           NUMERIC NOT NULL, 
    LEG_MATERIAL NUMERIC, 
    CONSTRAINT TABLES_PK PRIMARY KEY (ID)
);

INSERT INTO TABLES(ID, LEG_MATERIAL) VALUES (1, 1);

Now let's try to fetch the table having id 1 with following code:

Table table = tableDAO.get(1L);

this will cause hibernate to execute the SQL query:

select table0_.id as id0_1_, table0_.LEG_MATERIAL as LEG2_0_1_, materialty1_.id as id1_0_, materialty1_.description as descript3_1_0_ from TABLES table0_ left outer join DICTIONARIES materialty1_ on table0_.LEG_MATERIAL=materialty1_.id where table0_.id=?

with parameter 1 (table id)

which leads to the following result set:

+--------+-----------+--------+----------------+
| id0_1_ | LEG2_0_1_ | id1_0_ | descript3_1_0_ |
+--------+-----------+--------+----------------+
|      1 |         1 |      1 | Wood           |
|      1 |         1 |      1 | SOT1           |
+--------+-----------+--------+----------------+

as you see - there is missing discriminator part of where clause for the material type

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