Spring Data/JPS (N+1) 具有 OneToOne 关联的 SELECT

Question

在我的Spring数据应用中我运行进入（N+1）选择问题。

我有以下 Spring 个数据实体：

@Entity
@Table(name = "card_categories")
public class CardCategory extends BaseEntity implements Serializable {

    @Id
    @SequenceGenerator(name = "card_categories_id_seq", sequenceName = "card_categories_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "card_categories_id_seq")
    private Long id;

    private String name;
...

}

@Entity
@Table(name = "levels")
public class Level extends BaseEntity implements Serializable {

    @Id
    @SequenceGenerator(name = "levels_id_seq", sequenceName = "levels_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "levels_id_seq")
    private Long id;

    private String name;
...
}

@Entity
@Table(name = "card_categories_levels")
public class CardCategoryLevel extends BaseEntity implements Serializable {

    @Id
    @SequenceGenerator(name = "card_categories_levels_id_seq", sequenceName = "card_categories_levels_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "card_categories_levels_id_seq")
    private Long id;

    @OneToOne
    @JoinColumn(name = "card_category_id")
    private CardCategory cardCategory;

    @OneToOne
    @JoinColumn(name = "level_id")
    private Level level;
...

}

空 Spring 数据存储库：

@Repository
public interface CardCategoryLevelRepository extends JpaRepository<CardCategoryLevel, Long> {
}

当我尝试通过 cardCategoryLevelRepository.findAll() 方法获取所有 CardCategoryLevel 实体时，它会为我的 card_categories_levels table.

中的每一行生成 3 个 SELECT

为了使用一个 JOIN 而不是 N+1 SELECT，我重新实现了我的 CardCategoryLevelRepository:

@Repository
public interface CardCategoryLevelRepository extends JpaRepository<CardCategoryLevel, Long> {

    @Query(value = "SELECT ccl FROM CardCategoryLevel ccl LEFT JOIN FETCH ccl.cardCategory cc LEFT JOIN FETCH ccl.level l where cc = :cardCategory and l = :level")
    CardCategoryLevel findByCardCategoryAndLevel(@Param("cardCategory") CardCategory cardCategory, @Param("level") Level level);

    @Override
    @Query(value = "SELECT ccl FROM CardCategoryLevel ccl LEFT JOIN FETCH ccl.cardCategory LEFT JOIN FETCH ccl.level")
    List<CardCategoryLevel> findAll();

}

但我不确定我是否以正确的最佳方式做到了。

请验证我的方法并告诉它是解决 Spring 数据中 OneToOne 关联的 (N+1) SELECT 问题的最佳解决方法，以及解决它的最佳方法是什么。

我应该保持原样还是可以转移到其他抽象.. 例如像 QueryDSL 或类似的东西？

Answer 1

感谢 Xtreme Biker 我用实体图和 QueryDSL 重新实现了我的解决方案

Spring Data/JPS (N+1) 具有 OneToOne 关联的 SELECT

Spring Data/JPS (N+1) SELECTs with OneToOne associations

spring

jpa

querydsl

spring-data

spring-data-jpa