JPA一对一映射FetchType.LAZY不起作用

Question

我有两个实体，如下面的

@Entity
@Table(name = "ticket")
public class Ticket {

    @OneToOne(fetch=FetchType.LAZY, targetEntity = com.vahana.entity.TicketBookingAdditionalInfo.class, mappedBy = "ticket", cascade = CascadeType.MERGE)
    private TicketBookingAdditionalInfo ticketBookingAdditionalInfo;

}

@Entity
@Table(name = "ticket_booking_additional_info")
public class TicketBookingAdditionalInfo {

    /** The ticket. */
    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.MERGE)
    @JoinColumn(name = "ticket_id", columnDefinition = "BIGINT UNSIGNED")
    private Ticket ticket;

}

我的票证表包含40,000多条记录，但是订票额外信息没有任何数据。只有在我要添加其他信息时，此表才会包含数据。

在选择票证表时，它会加入ticket_booking_additional_info表，并且该查询需要更多时间。

我在@OneToOne中添加了fetch = FetchType.LAZY，但仍需要很长时间才能响应。这是我的数据库中最耗时的查询。如何避免这个问题。请有人指导我。

使用mysql DB，

Answer 1

@Entity
@Table(name = "ticket")
public class Ticket {

    //Default is lazy
    @OneToMany(mappedBy = "ticket", cascade = CascadeType.MERGE)
    private List<TicketBookingAdditionalInfo> ticketBookingAdditionalInfo;

}

@Entity
@Table(name = "ticket_booking_additional_info")
public class TicketBookingAdditionalInfo {

    // The ticket. 
    //Default is eager
    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.MERGE)
    @JoinColumn(name = "ticket_id", columnDefinition = "BIGINT UNSIGNED")
    private Ticket ticket;

}

注意 如果您有ManyToOne，则反向关系是OneToMany，如果您有OneToOne，则反之为OneToOne。您应该看到this教程

• OneToOne
的示例
• OneToMany
的示例
• ManyToOne
的示例