标准 API 按嵌套聚合排序属性

Question

如何通过聚合嵌套属性实现对象排序？我有一个 Photographer 实体，其中有很多 PhotographerPrice 实体（一对多），BigDecimal 属性称为 pricePerHour。当我检索摄影师时，我想按他们所拥有的最低价格对他们进行排序。

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Photographer> cq = cb.createQuery(Photographer.class);
Root<Photographer> root = cq.from(Photographer.class);
List<Predicate> predicates = new ArrayList<>(); // I have a lot of predicates which set if data was present by client

我尝试对 PhotographerPrice 进行子查询，然后在根目录中排序

Subquery<BigDecimal> subquery = cq.subquery(BigDecimal.class);
Root<PhotographerPrice> from = subquery.from(PhotographerPrice.class);
Predicate and = cb.and(
        cb.equal(root.get(Photographer_.id), from.get(PhotographerPrice_.photographer).get(Photographer_.id)),
        cb.isNotNull(from.get(PhotographerPrice_.pricePerHour))
);
subquery.correlate(root);
subquery.where(and);
subquery.select(cb.min(from.get(PhotographerPrice_.pricePerHour)));
subquery.groupBy(from.get(PhotographerPrice_.photographer).get(Photographer_.id));

...

cq.orderBy(cb.asc(subquery));

但是，正如我意识到的那样，不允许使用 order by 子查询。

那么，我该如何使用 Criteria API:

来实现类似的东西

select *
  from photographer p
  order by (
    select min(price_per_hour) minPrice
      from photographer_price pp
      where p.id = pp.photographer_id
        and pp.photo_per_hour is not null
      group by photographer_id
    );

当我尝试使用 Join 方法实现它时，我的结果列表中有重复项。

是否可以使用 Criteria API 来实现它？也许还有另一种工具可以更方便地从数据库中过滤实体？我有很多用于过滤和排序的不同参数，这些参数与嵌套属性有关，有时甚至与嵌套在嵌套属性.

中有关

我找到的唯一解决方法：

ListJoin<Photographer, PhotographerPrice> join = root.join(Photographer_.photographerPrices);
Expression<BigDecimal> min = cb.min(join.get(PhotographerPrice_.pricePerHour));
cq.orderBy(cb.desc(min));
cq.groupBy(root.get(Photographer_.id));

但我不确定分组依据。有没有可能稍后出现一些故障排除？

Answer 1

我发现的方法适用于我的案例

使用 Min 聚合函数左连接到 PhotographerPrice，然后根据此聚合的结果进行排序：

ListJoin<Photographer, PhotographerPrice> photographerPriceJoin = root.join(Photographer_.photographerPrices);
Expression<BigDecimal> min = cb.min(photographerPriceJoin.get(PhotographerPrice_.pricePerHour));
if (photographerCatalogFilter.getDirection().isDescending()) {
    orderList.add(cb.desc(min));
} else {
    orderList.add(cb.asc(min));
}

标准 API 按嵌套聚合排序属性

Criteria API Ordering by nested aggregated property

java

spring

hibernate

criteria-api

spring-data-jpa

标准 API 按嵌套聚合排序 属性

Criteria API Ordering by nested aggregated property

java

spring

hibernate

criteria-api

spring-data-jpa

标准 API 按嵌套聚合排序属性