SQLAlchemy：关系关系的急切加载关系答案

【问题标题】：SQLAlchemy : eager loading relationships of relationships of relationshipSQLAlchemy：关系关系的急切加载关系
【发布时间】：2018-10-10 04:31:47
【问题描述】：

我有这个结构：

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，我无法编写 1 个查询（我总是以循环和多个查询告终）来一次急切地加载所有这些信息：

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

【问题讨论】：

标签： python sqlalchemy eager-loading

【解决方案1】：

您可以尝试仅在查询中显式加载项目，而不是将其硬编码到您的关系中。像这样的：

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

【讨论】：