Hello,
In my project I have 3 applications, and I'm trying to split them across 2
databases.
More specifically 2 of the apps and Django "auth" application should work
with the first database,
and the last application should remain in the second database.
These are the DB settings:
DATABASE_ROUTERS = [
'<PATH_TO_ROUTER>.PrimaryRouter',
'<PATH_TO_ROUTER>.ValidationRouter'
]
DATABASES = {
'default': {},
'primary': {
'NAME': 'primary',
'ENGINE': 'django.db.backends.postgresql',
'USER': '<DB_USER>',
'PASSWORD': '<DB_PASS>',
'HOST': 'localhost',
},
'validations': {
'NAME': 'validations',
'ENGINE': 'django.db.backends.postgresql',
'USER': '<DB_USER>',
'PASSWORD': '<DB_PASS>',
'HOST': 'localhost',
}
}
Therefore these are the class routers:
class PrimaryRouter:
"""
Router to control all database operations for the following
applications:
- first_model
- second_model
- auth
"""
def db_for_read(self, model, **hints):
if model._meta.app_label == 'auth' or \
model._meta.app_label == 'first_model' or \
model._meta.app_label == 'second_model':
return 'primary'
return None
def db_for_write(self, model, **hints):
if model._meta.app_label == 'auth' or \
model._meta.app_label == 'first_model' or \
model._meta.app_label == 'second_model':
return 'primary'
return None
def allow_relation(self, first_object, second_object, **hints):
if first_object._meta.app_label == 'auth' or \
second_object._meta.app_label == 'auth':
return True
if first_object._meta.app_label == 'first_model' or \
second_object._meta.app_label == 'first_model':
return True
if first_object._meta.app_label == 'second_model' or \
second_object._meta.app_label == 'second_model':
return True
return None
def allow_migrate(self, db, app_label, model_name=None, **hints):
if app_label == 'auth' or \
app_label == 'first_model' or \
app_label == 'second_model':
return db == 'primary'
return None
class ValidationRouter:
"""
Router to control all database operations for the following
applications:
- fourth_model
"""
def db_for_read(self, model, **hints):
if model._meta.app_label == 'fourth_model':
return 'validations'
return None
def db_for_write(self, model, **hints):
if model._meta.app_label == 'fourth_model':
return 'validations'
return None
def allow_relation(self, first_object, second_object, **hints):
if first_object._meta.app_label == 'fourth_model' or \
second_object._meta.app_label == 'fourth_model':
return True
return None
def allow_migrate(self, db, app_label, model_name=None, **hints):
if app_label == 'fourth_model':
return True
return None
When I run migration on the first database "primary", everything is working.
But on the second database I'm getting the following exception:
django.db.utils.ProgrammingError: relation "auth_user" does not exist
*The question *- do I need to also specify the "auth" Django application in
the second DB router "validations",
or there's something wrong with my setup ?
According to Django docs for version 2.1, this kind of setup is working
- https://docs.djangoproject.com/en/2.1/topics/db/multi-db/ .
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