JavaspringhibernateJPA@ManyToAllfindAll()在大資料上速度很慢，創建了許多子查詢

我有 2 個班級，Aircraft并且具有從到Operator的一對多關系。來自 JPA 存盤庫的對表（大約 10k 行）的呼叫運行速度很快，只需幾秒鐘，但對表（大約 65k 行）的呼叫有時需要幾分鐘才能執行。OperatorAircraftfindAll()OperatorfindAll()Aircraft

另外，我注意到運算子上的操作僅在控制臺中findAll()生成 1 個休眠查詢，而在飛機上，它會在飛機表上生成 1 個查詢，并且對具有約束的運算子生成許多其他查詢，我認為這不是想要的。SELECTSELECTSELECTwhere operator0_.id=?

從 Controller 類到 Service 類的 GET 請求呼叫 findAll()，結果用于將 Aircraft 物件映射到 AircraftDTO 物件，該物件還包括操作員名稱。

如何解決此問題以使運行中的findAll()查詢Aircraft更快？

注意：由于在這種情況下缺乏相關性，一些類屬性被洗掉

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@Entity
public class Aircraft implements Serializable {
    @Id
    @GeneratedValue(
            strategy = GenerationType.SEQUENCE,
            generator = "aircraft_sequence"
    )
    @SequenceGenerator(
            name = "aircraft_sequence",
            allocationSize = 1
    )
    @Column(nullable = false, updatable = false)
    private Long id;
    @ManyToOne
    @JoinColumn(name="operator_id", nullable=false)
    private Operator operator;
    private String registration;
}

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@Entity
public class Operator implements Serializable {
    @Id
    @GeneratedValue(
            strategy = GenerationType.SEQUENCE,
            generator = "operator_sequence"
    )
    @SequenceGenerator(
            name = "operator_sequence",
            allocationSize = 1
    )
    @Column(nullable = false, updatable = false)
    private Long id;
    private String name;
    @OneToMany(fetch = FetchType.LAZY, mappedBy="operator")
    @JsonIgnore
    private Set<Aircraft> aircraft;
}

public interface AircraftRepository extends JpaRepository<Aircraft, Long> {
}

public interface OperatorRepository extends JpaRepository<Operator, Long> {
}

Hibernate: select aircraft0_.id as id1_0_, aircraft0_.operator_id as operator7_0_, aircraft0_.registration as registra5_0_ from aircraft aircraft0_
Hibernate: select operator0_.id as id1_2_0_, operator0_.name as name12_2_0_ from operator operator0_ where operator0_.id=?
Hibernate: select operator0_.id as id1_2_0_, operator0_.name as name12_2_0_ from operator operator0_ where operator0_.id=?
Hibernate: select operator0_.id as id1_2_0_, operator0_.name as name12_2_0_ from operator operator0_ where operator0_.id=?
Hibernate: select operator0_.id as id1_2_0_, operator0_.name as name12_2_0_ from operator operator0_ where operator0_.id=?
Hibernate: select operator0_.id as id1_2_0_, operator0_.name as name12_2_0_ from operator operator0_ where operator0_.id=?
Hibernate: select operator0_.id as id1_2_0_, operator0_.name as name12_2_0_ from operator operator0_ where operator0_.id=?
Hibernate: select operator0_.id as id1_2_0_, operator0_.name as name12_2_0_ from operator operator0_ where operator0_.id=?
...and so on

uj5u.com熱心網友回復：

問題是存在一個回圈依賴，通過覆寫類findAll()中的AircraftRepository并包括JOIN FETCH

public interface AircraftRepository extends JpaRepository<Aircraft, Long> {
    @Override
    @Query(value = "SELECT distinct a"  
            "         FROM Aircraft a "  
            "              JOIN FETCH a.operator ")
    List<Aircraft> findAll();
}

標籤：爪哇mysql春天休眠jpa

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