spring jpa 嵌套投影生成不正确的查询 [英] spring jpa nested projection generating incorrect query

问题描述

让我们考虑这些实体

@Entity
public class Room{

  @Id
  private Integer id;

  private String number;

  private String floor;

  @ManyToOne
  private RoomType roomType;

  // Setters & Getters  
}

@Entity
public class RoomType{

  @Id
  private Integer id;

  private String name;

  private String description;

  private Boolean enabled;

  // Setters & Getters  
}

还有这个用于与存储库类一起投影的接口

And also this interface for projection alongside repository class

public interface RoomList{

    public Number getId();

    public String getNumber();

    public RoomType getRoomType();

    interface RoomType {
        String getName();
    }   

}

@Repository
public interface RoomRepository extends JpaRepository<Room,Integer>{

    public Collection<RoomList> findAllProjectedBy();

}

现在，如果我查看生成的 SQL

Now if I look at generated SQL

select
    room0_.id as col_0_0_,
    room0_.number as col_1_0_,
    roomtype1_.id as id1_3_,
    roomtype1_.description as descript2_3_,
    roomtype1_.enabled as isActive3_3_,
    roomtype1_.name as name5_3_ 
from
    Room room0_ 
inner join
    roomType roomtype1_ 
        on room0_.roomType_id=roomtype1_.id

生成的查询应该是这样的

select
    room0_.id as col_0_0_,
    room0_.number as col_1_0_,
    roomtype1_.name as name5_3_ 
from
    Room room0_ 
inner join
    roomType roomtype1_ 
        on room0_.roomType_id=roomtype1_.id

有人可以解释这种行为还是这是一个错误?我们还有什么其他选择可以达到这种结果.我已经尝试过 JPA entitygraph，但是在 hibernate 中还没有完全支持图形类型提取，我也不想使用构造函数 jpql 查询.谢谢！

Can someone explain this behaviour or either this is a bug ? also what other options do we have achieve this kind of result. I already tried JPA entitygraph but graph type fetch is not yet fully supported in hibernate, i don't want to use constructor jpql query either. Thanks !

推荐答案

如果理解正确，问题是会选择更多的属性/列来填充投影.

If understand correctly the concern is that more attributes/columns get selected than necessary to fill the projections.

正如我刚刚在 issue DATAJPA-1218 中所描述的，这就是投影的工作原理当前的 Spring 数据.引用实体的属性不限于投影中使用的属性.

As I just described in issue DATAJPA-1218 this is just how projections work in Spring Data currently. The attributes of referenced entities do not get limited to those used in the projection.

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