Question

我在ORM的Spring Boot应用程序中将spring-data-jpa与hibernate一起使用。我与OneToOne关系生成N + 1查询时遇到问题，而我不需要获取oneToOne对象。

我的OneToOne关系很容易获取，我尝试将懒惰与获取模式结合使用，但仍然无法获取它仅生成一个查询。

这是实体和查询的代码：

@Entity
@Table(name = "item")
public class Item implements Serializable {

   @Id
   @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
   @SequenceGenerator(name = "sequenceGenerator")
    private Long id;

   @Column(name = "number")
   private String number;

   @Column(name = "date")
   private LocalDate date;

    @OneToOne(mappedBy = "item", fetch = FetchType.EAGER)
    @JsonIgnore
    private Status status;

}

@Entity
@Table(name = "status")
public class Status implements Serializable {

   @Id
   @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
   @SequenceGenerator(name = "sequenceGenerator")
    private Long id;

   @OneToOne(fetch = FetchType.EAGER)
   @JoinColumn(unique = true)
   private Item item;

}

这是存储库中的查询：

@Query(value = "SELECT * FROM ( SELECT  number, MAX(date) AS date FROM item WHERE date < ? GROUP BY number) AS latest_it INNER JOIN item ON item.number = latest_it.number AND item.date = latest_it.date", nativeQuery = true)
List<Item> findLatestByNumberAndDate(LocalDate localDate);

运行查询时，我听到了查询音：

select status0_.id ... from status status0_ left outer join item item1_ on status0_.item_id=item1_.id left outer join status status2_ on item1_.id=status2_.item_id where status0_.item_id=?

我希望看到的只是执行存储库中定义的查询。这个问题确实是性能上的痛苦。

您对此有何暗示？

谢谢

一对一关系上的休眠N + 1问题

0 个答案: