python - SQL炼金术 : eager loading relationships of relationships of relationship

Question

我有这样的结构:

class User(DeclarativeBase):
   ...
   teamMemberships = orm.relationship("TeamXREF",backref="user",lazy = "dynamic")


class TeamXREF(DeclarativeBase):
   ...


class Team(DeclarativeBase):
   ...
   name=db.Column(String)
   teamMembers = orm.relationship("TeamXREF",backref="team",lazy = "dynamic")

但是，我无法在 1 个查询中编写(我总是以循环和多个查询结束)急切地一次加载所有这些信息:

• user.teamMemberships
• user.teamMemberships.team
• user.teamMemberships.team.teamMembers
• user.teamMemberships.team.teamMembers.user

Answer 1

您可能会尝试在查询中显式加载项目，而不是将其硬编码到您的关系中。像这样:

from sqlalchemy.orm import joinedload
Session.query(User).options(joinedload('teamMemberships').joinedload('team').joinedload('teamMembers').joinedload('user'))

http://docs.sqlalchemy.org/en/improve_toc/orm/loading_relationships.html#loading-along-paths