条件失败的左连接提取 [英] Left join fetch with condition fails

问题描述

我有以下 HQL 查询：

return entityManager().createQuery(
    "SELECT page FROM ProjectPage page"
  + " left join fetch page.categorySet as category              "
  + " where page.id = :id " 
  + " and  category.parentCategory is null "
  + " and  (category.status != :status_val) " 
  ,ProjectPage.class).setParameter("id", id)
  .setParameter("status_val", 1).getSingleResult();

问题是where子句中的条件失败，例如，查询返回类别对象状态为1，并且parentCategory不为null的类别对象，尽管我指定此约束如上所述!!

the problem is that the conditions in the where clause fails, for example, the query returns category objects whose status is 1 and category objects whose parentCategory is not null although i specified this constrains as stated above!!

推荐答案

查询返回 ProjectPage 对象与 categorySet 过滤掉基于其中条件，那么你的期望是错误的。如果 ProjectPage 具有给定ID的实例包含通过 where 子句条件的任何将作为整个对象返回 。这是通过设计，因为底层机制，缓存等需要。如果你需要满足一些条件的类别对象，你必须为它写一个单独的查询。

If you expect this query to return ProjectPage object with categorySet filtered out based on where conditions, then your expectations are wrong. If ProjectPage instance with given id contains any category that pass the where clause conditions, it will be returned as a whole object. This is by design, and needed because of underlying mechanisms, caching, etc. If you need category objects that fulfill some conditions, you'll have to write a separate query for that.

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