Hibernate 6查询生成错误：鉴别器条件位置异常问题

实体类定义 #

@Entity
@Table(name = "users")
public class User extends BaseEntity implements Serializable {

..

    @OneToMany(fetch = FetchType.EAGER, cascade = { CascadeType.MERGE, CascadeType.PERSIST }, mappedBy = "entity")
    private Set<UserUdfValue> properties = new HashSet<>();

..

}

@Entity
@DiscriminatorValue(UserUdfValue.UDFID)
public class UserUdfValue extends ValueBase {

    private static final long serialVersionUID = -898152830344556386L;

    public final static String UDFID = "1";

    @ManyToOne(fetch=FetchType.LAZY, cascade = {})
    @JoinColumn(name = "entity_id", nullable = false)
    private User entity;

    public User getEntity() {
        return entity;
    }

    public void setEntity(User entity) {
        this.entity = entity;
    }

}


@Entity(name = "udf_value")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "target_type", discriminatorType = DiscriminatorType.INTEGER)
@DiscriminatorOptions(force = false)
public abstract class ValueBase implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    
...

}

问题现象 #

Hibernate 5.6 生成的预期SQL #

根据ID查询User时，鉴别器条件被放在JOIN子句中，查询逻辑符合预期：

SELECT *
FROM users user0_
LEFT OUTER JOIN udf_value properties14_ ON user0_.id = properties14_.entity_id
    AND properties14_.target_type = 1
WHERE user0_.id = ?

Hibernate 6 生成的错误SQL #

升级到Hibernate 6后，鉴别器条件被移至WHERE子句，导致查询结果不符合预期：

SELECT *
FROM users u1_0
LEFT JOIN udf_value p2_0 ON u1_0.id = p2_0.entity_id
WHERE p2_0.target_type = 1
    AND u1_0.id = ?

该SQL会过滤掉没有对应UserUdfValue记录的User，完全违背了LEFT JOIN的设计意图。

问题确认 #

该问题已被Hibernate官方确认为Bug。

内容的提问来源于stack exchange，提问作者gaetann