SQLAlchemy中两个关联表的多个连接？

Question

我有这段（简化但有效的）代码来处理工作区的概念，其中每个工作区都可以有成员（分配到工作区的用户）和团队（也属于工作区）。

import json

from datetime import datetime
from sqlalchemy import create_engine  
from sqlalchemy import Column, String, DateTime, Boolean, Integer, ForeignKey
from sqlalchemy.ext.declarative import declarative_base  
from sqlalchemy.orm import sessionmaker, relationship, backref


db_uri = "postgresql://postgres:postgres@127.0.0.1/test_db"

db = create_engine(db_uri)  
Base = declarative_base()


class UserWorkspaceRole(Base):
    __tablename__ = "user_workspace_role"
    user_id = Column(Integer, ForeignKey('user.id'), primary_key=True)
    workspace_id = Column(Integer, ForeignKey('workspace.id'), primary_key=True)
    role_id = Column(Integer, ForeignKey('role.id'), primary_key=True)
    

class UserWorkspaceTeam(Base):
    __tablename__ = "user_workspace_team"
    user_id = Column(Integer, ForeignKey('user.id'), primary_key=True)
    workspace_id = Column(Integer, ForeignKey('workspace.id'), primary_key=True)
    team_id = Column(Integer, ForeignKey('team.id'), primary_key=True)


class User(Base):
    __tablename__ = "user"
    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String)
    team_workspaces = relationship(UserWorkspaceTeam, cascade="all, delete-orphan", backref="user")
    role_workspaces = relationship(UserWorkspaceRole, cascade="all, delete-orphan", backref="user")


class Workspace(Base):
    __tablename__ = "workspace"
    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String)
    team_users = relationship(UserWorkspaceRole, cascade="all, delete-orphan", backref="workspace")
    role_users = relationship(UserWorkspaceTeam, cascade="all, delete-orphan", backref="workspace")


class Role(Base):
    __tablename__ = "role"
    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String)
    role = relationship(UserWorkspaceRole, cascade="all, delete-orphan", backref="role")


class Team(Base):
    __tablename__ = "team"
    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String)
    team = relationship(UserWorkspaceTeam, cascade="all, delete-orphan", backref="team")


Session = sessionmaker(db)  
session = Session()

Base.metadata.create_all(db)
#Base.metadata.drop_all(db)

# Add roles
role_owner = Role(name="owner")
role_member = Role(name="member")
roles = [role_owner, role_member]
session.add_all(roles)
session.commit()

# Add teams
team_1 = Team(name="Team_1")
team_2 = Team(name="Team_2")
teams = [team_1, team_2]
session.add_all(teams)
session.commit()

# Add users
user1 = User(name="User_1")
user2 = User(name="User_2")
user3 = User(name="User_3")
users = [user1, user2, user3]
session.add_all(users)
session.commit()


workspace1 = Workspace(name="Apple")

test1 = UserWorkspaceRole(user=user1,workspace=workspace1, role_id="1")
test2 = UserWorkspaceRole(user=user2,workspace=workspace1, role_id="2")
test3 = UserWorkspaceRole(user=user3,workspace=workspace1, role_id="2")
test4 = UserWorkspaceTeam(user=user1,workspace=workspace1, team_id="1")
test5 = UserWorkspaceTeam(user=user1,workspace=workspace1, team_id="2")

records = [test1, test2, test3, test4, test5]
session.add_all(records)

session.commit()

x = session.query(UserWorkspaceRole).join(User).join(Workspace).join(Role).filter(Workspace.id == '1').all()

members = []

for n in range(len(x)):
    members.append(
            {
            "workspace": x[n].workspace.id,
            "name": x[n].user.name,
            "role": x[n].role.name
            }
        )
print(json.dumps(members, indent=4))

它给出以下输出：

[
    {
        "workspace": 1,
        "name": "User_1",
        "role": "owner"
    },
    {
        "workspace": 1,
        "name": "User_3",
        "role": "member"
    },
    {
        "workspace": 1,
        "name": "User_2",
        "role": "member"
    }
]

我想要实现的是在列表中的每个字典中添加用户在某个工作区中所属的团队。我可以通过一个查询来实现这一点吗？我也尝试加入 UserWorkspaceTeam，但可能我遗漏了一些东西（我是 db 的新手）。

我想要的输出应该是这样的：

[
    {
        "workspace": 1,
        "name": "User_1",
        "role": "owner",
        "teams": [
            {"id": "1", "name": "Team_1"},
            {"id": "2", "name": "Team_2"}
        ]
    },
    {
        "workspace": 1,
        "name": "User_3",
        "role": "member"
    },
    {
        "workspace": 1,
        "name": "User_2",
        "role": "member"
    }
]

我怎样才能做到这一点？

Answer 1

在您的for 循环中使用range() 函数时，您指定的上限不足一。尝试像以前一样加入UserWorkspaceTeam，但这次添加到范围函数的上限，允许您到达最后一个索引。希望这会有所帮助。

x = session.query(UserWorkspaceRole).join(User).join(Workspace).join(Role).join(UserWorkspaceTeam).filter(Workspace.id == '1').all()

members = []

# The range() function includes values from 0 until a bound you specify but not including it.
for n in range(len(x)+1):
    members.append(
        {
        "workspace": x[n].workspace.id,
        "name": x[n].user.name,
        "role": x[n].role.name,
        }
    )
print(json.dumps(members, indent=4))