避免从Hibernate中选择N + 1(Avoid N+1 selects from Hibernate)

 在我的项目中，我们有hbm.xml文件，fetch =“select”表示所有关系表的一对多。 
 
 例如：一所学校有很多教室，一间教室有很多孩子 
 
 所以在我的hbm文件中 
 
 school.hbm.xml 
 <set name =“classrooms” lazy =“false”fetch =“select” > 
 
 classroom.hbm.xml 
 <set name =“children” lazy =“false”fetch =“select” > 
 
 有一种情况我只想获取基于教室div ='A'的学校列表。 但是由于这种映射，hibernate正在为教室做选择，在这种情况下我不想要。 
 
 请帮助我如何避免在课堂上做不必要的选择。 无论如何都要覆盖这种获取模式，只能加入学校和教室，而不是孩子 
 
 我试过多种选择，但没有运气。 非常感谢您的投入。 

In my project we have hbm.xml file which is fetch="select" for one-to-many for all relation tables.
 
For ex: One school is having many classrooms and one classroom will have many children
 
so in my hbm file 
 
school.hbm.xml 
 <set name="classrooms" lazy="false" fetch="select">
 
classroom.hbm.xml 
 <set name="children" lazy="false" fetch="select">
 
There is a case where I want to fetch only list of schools which are based on classroom div = 'A'. But because of this mapping hibernate is doing select for classroom as well which I don't want in this case.
 
Please help me how can I avoid doing unnecessary select with classroom. Is there anyway to override this fetch mode and join only with School and classroom and not with children
 
I tried with multiple options but no luck. Really appreciate for your inputs. 

原文：https://stackoverflow.com/questions/32364321