我有一个名为direct_message的表，它存储了用户之间的直接消息列表，如下所示：
| ID|父ID|收件人_ID|发送者_ID|标题|消息|发送时间|READ_AT
我想发回一个由SENT_AT排序的最近消息的列表。我使用JPA，所以查询将基于RECIPIENT_ID发送回消息列表，如下所示：

@Repository
@Transactional(readOnly = true)
public interface DirectMessageRepository extends JpaRepository<DirectMessage, Long> {
    Page<DirectMessage> findDirectMessageByRecipientId(Long recipientId, Pageable pageable);
}

这是我的Entity类：

@Getter
@Setter
@NoArgsConstructor
@Entity
@Table(name = "direct_message")
public class DirectMessage {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "direct_message_sequence")
    @SequenceGenerator(name = "direct_message_sequence", sequenceName = "direct_message_sequence", allocationSize = 1)
    @Column(name = "id", nullable = false)
    private Long id;
    @ManyToOne
    @JoinColumn(name = "parent_id")
    private DirectMessage parent;
    @ManyToOne
    @JoinColumn(nullable = false, name = "sender_id")
    private User sender;
    @ManyToOne
    @JoinColumn(nullable = false, name = "recipient_id")
    private User recipient;
    private String title;
    @Lob
    @Column(columnDefinition = "TEXT")
    @Size(max = 4000)
    private String message;
    @Column(name = "sent_at")
    private LocalDateTime sentAt;
    private Boolean isRead = false;
    @Column(name = "read_at")
    private LocalDateTime readAt;
    @Column(name = "can_reply")
    private Boolean canReply;
}

然而，我的问题是，它将发送回一条作为父消息的消息，以及一条包含它作为嵌套父消息的子消息。下面是一个简化的例子（省略了发送者、接收者和其他数据）：

[{
    "id": 1,
    "parent": null,
    "recipient": {},
    "sender": {},
    "title": "Message thread",
    "message": "Hello"
}, {
    "id": 2,
    "parent": {
        "id": 1,
        "parent": null,
        "recipient": {},
        "sender": {},
        "title": "Message thread",
        "message": "Hello"
    },
    "recipient": {},
    "sender": {},
    "title": "Message thread",
    "message": "This is the reply"
}]

因此，正如您所看到的，父消息（ID 1）是重复的（作为它自己的行，也作为另一条消息的父消息，该消息是该消息的子消息）。在JPA中有没有一种方法可以消除重复数据？并且只在它不是另一个消息线程的一部分时才发送回消息？或者，如果在JPA中不可能，是否有一个SQL查询可以完成这项工作？