我需要用 spring 資料 jpa 和標準 api 撰寫一個動態查詢，但休眠生成不必要的交叉連接和重復結果。
物體類
@Id
@GeneratedValue(generator = "uuid")
@GenericGenerator(name = "uuid", strategy = "org.hibernate.id.UUIDGenerator")
private String id;
private String accountId;
@CreationTimestamp
private LocalDateTime createdTs;
@UpdateTimestamp
private LocalDateTime updatedTs;
詢問：
CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Long> query = cb.createQuery(Long.class);
Root<FavouriteItemEntity> root = query.from(MyEntity.class);
Path<String> accountIdPath = root.get("accountId");
List<Predicate> predicates = new ArrayList<>();
predicates.add(cb.equal(accountIdPath, accountId));
query.select(cb.count(query.from(MyEntity.class)));
query.where(predicates.toArray(new Predicate[0]));
return entityManager.createQuery(query)
.getSingleResult();
Hql 生成交叉連接和重復結果
Hibernate: select count(favouritei1_.id) as col_0_0_ from favourite favouritei0_ cross join favourite favouritei1_ where favouritei0_.account_id=?
代替
Hibernate: select count(f.id) from favourite f where f.account_id = ?
為什么會這樣？
uj5u.com熱心網友回復：
這是使用 Criteria 查詢時的常見錯誤。您呼叫了query.from兩次，因此是交叉連接。改為呼叫一次：
query.select(cb.count(root));
轉載請註明出處，本文鏈接：https://www.uj5u.com/shujuku/395773.html
標籤：爪哇 sql PostgreSQL的 休眠 弹簧数据-jpa