带分页的Spring-Data FETCH JOIN不起作用

Question

我正在尝试使用HQL使用JOIN FETCH来获取我的实体以及子实体，如果我想要所有结果，这可以正常工作，但是如果我想要一个Page，则不是这样

我的实体是

@Entity
@Data
public class VisitEntity {

    @Id
    @Audited
    private long id;

    .
    .
    .

    @OneToMany(cascade = CascadeType.ALL,)
    private List<VisitCommentEntity> comments;
}

并且由于我有数百万次的访问，因此我需要使用Pageable，并且希望在单个数据库查询中提取注释：

@Query("SELECT v FROM VisitEntity v LEFT JOIN FETCH v.comments WHERE v.venue.id = :venueId and ..." )
public Page<VisitEntity> getVenueVisits(@Param("venueId") long venueId,...,
        Pageable pageable);

该HQL调用引发以下异常：

Caused by: java.lang.IllegalArgumentException: org.hibernate.QueryException: query specified join fetching, but the owner of the fetched association was not present in the select list [FromElement{explicit,not a collection join,fetch join,fetch non-lazy properties,classAlias=null,role=com.ro.lib.visit.entity.VisitEntity.comments,tableName=visitdb.visit_comment,tableAlias=comments1_,origin=visitdb.visit visitentit0_,columns={visitentit0_.visit_id ,className=com.ro.lib.visit.entity.VisitCommentEntity}}] [select count(v) FROM com.ro.lib.visit.entity.VisitEntity v LEFT JOIN FETCH v.comments WHERE v.venue.id = :venueId and (v.actualArrival > :date or v.arrival > :date)]
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1374)
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1310)
at org.hibernate.ejb.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:309)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

一旦我删除分页，一切正常

@Query("SELECT v FROM VisitEntity v LEFT JOIN FETCH v.comments WHERE v.venue.id = :venueId and  ..." )
public List<VisitEntity> getVenueVisits(@Param("venueId") long venueId,...);

显然问题是来自Spring-Data的count查询，但是我们如何解决呢？

Answer 1

最简单的方法是使用批注的countQuery属性@Query来提供要使用的自定义查询。

@Query(value = "SELECT v FROM VisitEntity v LEFT JOIN FETCH v.comments …",
       countQuery = "select count(v) from VisitEntity v where …")
List<VisitEntity> getVenueVisits(@Param("venueId") long venueId, …);