[英]Mapping Error in SQLAlchemy while using a Foreign Key
我有兩個 SQLAlchemy 模型,其中一個由主鍵引用。
這是我的父模型:
try:
from sqlalchemy import Column, Integer, Enum, DateTime, String, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker, relationship
from sqlalchemy.orm import validates, backref
import datetime
from lib.dbConnector import Session
from werkzeug.security import generate_password_hash
except ImportError as err:
raise err
Base = declarative_base()
class users_table(Base):
__tablename__ = 'users_table'
userid = Column(String(50), unique= True, primary_key= True, nullable= False)
username = Column(String(500), unique= True, nullable= False)
password = Column(String(500), nullable= False)
email = Column(String(500), nullable= False, unique= True)
role = Column(String(10), default= 'user', nullable= False)
created_on = Column(DateTime, nullable= False, default= datetime.datetime.utcnow)
updated_on = Column(DateTime, nullable= False, default= datetime.datetime.utcnow)
這是我的子表:
try:
from sqlalchemy import Column, Integer, Enum, DateTime, String, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker, relationship
from sqlalchemy.orm import validates
import datetime
from lib.dbConnector import Session
except ImportError as err:
raise err
Base = declarative_base()
class user_status_table(Base):
__tablename__ = 'user_status_table'
id = Column(Integer, primary_key= True, nullable= False, unique= True, autoincrement=True)
userid = Column(String(50), ForeignKey('models.usersModel.users_table.userid'), nullable= False, unique= True)
status = Column(String(50), default= 'active', nullable= False)
updated_on = Column(DateTime, nullable= False, default= datetime.datetime.utcnow)
userid = relationship('models.usersModel.users_table.users_table', foreign_keys=userid)
在運行我的服務器時,我收到以下錯誤
"One or more mappers failed to initialize - can't proceed with initialization of other mappers. Triggering mapper: 'Mapper|user_status_table|user_status_table'. Original exception was: mapper"
誰能建議我在這里做錯了什么? 這就是我提交交易的地方
userdata = usersModel.users_table(userid, username, password, email, role)
try:
self.session.add(userdata)
self.session.flush()
userstatusdata = userstatusModel.user_status_table(userdata.userid, 'active')
self.session.add(userstatusdata)
self.session.commit()
except:
self.session.rollback()
raise
在我們開始回答您的問題之前,有幾點說明:
我用代碼創建了兩個文件,清理干凈以刪除我肯定不需要的東西。 usermodel.py 包含以下內容:
from sqlalchemy import Column, Integer, Enum, DateTime, String, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class users_table(Base):
__tablename__ = 'users_table'
userid = Column(String(50), unique= True, primary_key= True, nullable= False)
username = Column(String(500), unique= True, nullable= False)
userstatus.py 包含:
from usermodel import Base, users_table
from sqlalchemy import Column, Integer, Enum, DateTime, String, ForeignKey
from sqlalchemy.orm import relationship
class user_status_table(Base):
__tablename__ = 'user_status_table'
id = Column(Integer, primary_key= True, nullable= False, unique= True, autoincrement=True)
userid = Column(String(50), ForeignKey('users_table.userid'), nullable= False, unique= True)
user = relationship('users_table')
一些變化突出顯示:
Base
變量的創建,並在 userstatus.py 中導入了該變量,因此兩個表都在同一架構中。 我認為您不需要導入 usermodel,但我沒有檢查__tablename__
屬性識別表。 這不能以類名作為前綴。讓我們測試一下:
Python 3.6.5 (default, Mar 31 2018, 19:45:04) [GCC] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import usermodel
>>> import userstatus
>>> usr1 = usermodel.users_table(userid='You', username='Zacharia')
>>> stat1 = userstatus.user_status_table(id=1, user=usr1)
>>> stat1.user
<usermodel.users_table object at 0x7fa2ddbabfd0>
>>> stat1.user.userid
'You'
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