Question

由于注释@ManyToOne，我使用关联表在两个实体之间建立了一个简单的Hibernate @JoinTable映射。这是我的映射：

@Entity
public class Customer {

    private Long id;
    private Address address;

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


    @ManyToOne
    @JoinTable(
            name = "customer_address_association",
            joinColumns = @JoinColumn(name = "customer_id"),
            inverseJoinColumns = @JoinColumn(name = "address_id")
    )
    public Address getAddress() {
        return address;
    }

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

    public void setAddress(Address address) {
        this.address = address;
    }
}

和

@Entity
public class Address {

    private Long id;
    private String street;

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

    public String getStreet() {
        return street;
    }

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

    public void setStreet(String street) {
        this.street = street;
    }
}

当我查询“客户”实体时，总是会得到一个额外的左联接到联接表。例如，诸如SELECT c.id from Customer c之类的HQL查询生成以下SQL查询：select customer0_.id as col_0_0_ from customer customer0_ left outer join customer_address_association customer0_1_ on customer0_.id=customer0_1_.customer_id。

完整的源代码可以在这里找到：https://github.com/ndionisi/hibernate-extra-left-join

我用Hibernate 5.1、5.2和5.3复制它。有什么方法可以防止Hibernate生成对customer_address_association表的左联接？它会影响大型表的性能。

Hibernate产生多对多关联的额外左连接

0 个答案: