I am working on an application with two databases and two different
dbRouters. On migrating a model with a OneToOneField I get the following
error :
django.db.utils.OperationalError: (1824, "Failed to open the referenced
table 'auth_user'")
The auth dbRouter is for the [auth, sessions, contenttypes, admin] apps
while the Redford dbRouter is for the main app.
Below is the code for the routers :
*auth dbRouter*
class AuthRouter:
"""
A router to control all database operations on models in the
auth and contenttypes applications.
"""
route_app_labels = ('auth', 'contenttypes', 'sessions', 'admin')
def db_for_read(self, model, **hints):
"""
Attempts to read auth and contenttypes models go to auth_db.
"""
if model._meta.app_label in self.route_app_labels:
return "default"
return False
def db_for_write(self, model, **hints):
"""
Attempts to write auth and contenttypes models go to auth_db.
"""
if model._meta.app_label in self.route_app_labels:
return "default"
return False
def allow_relation(self, obj1, obj2, **hints):
"""
Allow relations if a model in the auth or contenttypes apps is
involved.
"""
if (obj1._meta.app_label in self.route_app_labels or
obj2._meta.app_label == 'julia' or 'redford'
):
return True
return None
def allow_migrate(self, db, app_label, model_name=None, **hints):
"""
Make sure the auth and contenttypes apps only appear in the
'auth_db' database.
"""
if db == 'default':
# Migrate Django core app models if current database is home
if app_label in ('auth','admin','sessions','contenttypes'):
return True
else:
return False
# Non Django core app models should not be migrated if
database is home
# Other database should not migrate Django core app models
elif app_label in ['auth','admin','sessions','contenttypes']:
return False
# Otherwise no opinion, defer to other routers or default database
return None
*Redford dbRouter*
class RedfordRouter(object):
route_app_labels = ('auth', 'contenttypes', 'sessions', 'admin')
def db_for_read(self, model, **hints):
if model._meta.app_label == 'redford':
return 'redford_db'
return False
def db_for_write(self, model, **hints):
if model._meta.app_label == 'redford':
return 'redford_db'
return False
def allow_relation(self, obj1, obj2, **hints):
if obj1._meta.app_label == 'redford' or obj2._meta.app_label ==
'auth':
return True
return None
def allow_migrate(self, db, app_label, model_name=None, **hints):
if db == 'default' or app_label in self.route_app_labels:
print(db, app_label)
return None
elif db == 'redford_db':
if app_label == 'redford':
return True
return False
return None
The code for the models is as below :
class Employer(models.Model):
emp_Name = models.OneToOneField(User, on_delete=models.CASCADE,
null=True)
emp_Company = models.CharField(max_length=100)
emp_Address = models.CharField(max_length=500)
emp_Tel = models.CharField(max_length=100)
emp_JobTitle = models.CharField(max_length=200, null=True)
emp_JobDesc = models.CharField(max_length=600, null=False)
def __str__(self):
return self.emp_Name
Hope we can work it out
regards
[image: --]
Maninder Kumar
[image: http://]about.me/maninder.s.kumar
<http://about.me/maninder.s.kumar?promo=email_sig>
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