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I have to use multiple databases in my project but there is a problem. Model can't see intended database accounts.db.
when i go localhost:port/admin/app/accounts it says me no such table: accounts. Model is looking for default database not accounts.db how can i do that?
I tried multiple things that I found on internet but nothing worked.
settings.py :
.....
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
},
'accounts': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'accounts.db')
}
}
.....
models.py:
.....
class Accounts(models.Model):
email = models.TextField(blank=True, null=True)
phone = models.TextField(blank=True, null=True)
name = models.TextField(blank=True, null=True)
password = models.TextField(blank=True, null=True)
verify = models.IntegerField(blank=True, null=True)
class Meta:
managed = False
db_table = 'accounts'
....
Environment:
Request Method: GET
Request URL: http://localhost:port/admin/hede/accounts/
Django Version: 1.11.23
Python Version: 2.7.15
Installed Applications:
['django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'hede']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware']
Traceback:
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/exception.py" in inner
41. response = get_response(request)
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in _get_response
187. response = self.process_exception_by_middleware(e, request)
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in _get_response
185. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in wrapper
552. return self.admin_site.admin_view(view)(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapped_view
149. response = view_func(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/views/decorators/cache.py" in _wrapped_view_func
57. response = view_func(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/sites.py" in inner
224. return view(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapper
67. return bound_func(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapped_view
149. response = view_func(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in bound_func
63. return func.__get__(self, type(self))(*args2, **kwargs2)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in changelist_view
1564. self.list_max_show_all, self.list_editable, self,
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/views/main.py" in __init__
79. self.get_results(request)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/views/main.py" in get_results
177. result_count = paginator.count
File "/usr/local/lib/python2.7/dist-packages/django/utils/functional.py" in __get__
35. res = instance.__dict__[self.name] = self.func(instance)
File "/usr/local/lib/python2.7/dist-packages/django/core/paginator.py" in count
79. return self.object_list.count()
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py" in count
364. return self.query.get_count(using=self.db)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py" in get_count
499. number = obj.get_aggregation(using, ['__count'])['__count']
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py" in get_aggregation
480. result = compiler.execute_sql(SINGLE)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/compiler.py" in execute_sql
899. raise original_exception
Exception Type: OperationalError at /admin/hede/accounts/
Exception Value: no such table: accounts
707
To use multiple databases you have to tell Django about the database server you will be using, but adding them in the settings.py.
Multiple databases
'default': {
'NAME': 'app_data',
'ENGINE': 'django.db.backends.postgresql',
'USER': 'postgres_user',
'PASSWORD': 's3krit'
},
'users': {
'NAME': 'user_data',
'ENGINE': 'django.db.backends.mysql',
'USER': 'mysql_user',
'PASSWORD': 'priv4te'
}
}
The migrate management command operates on one database at a time. By default, it operates on the default database, but by providing the --database option, you can tell it to synchronize a different database.
$ ./manage.py migrate --database=users
$ ./manage.py migrate --database=customers
You can manually select the database in your queries queries e.g
user = User(....)
user.save(using='users')
Customer.objects.all().using('users')
Using raw cursor
with connections['users'].cursor() as cursor:
cursor.execute("SELECT * FROM users__users")
As far as I know, your models can see the database, but aren't using 'accounts' database because it's set to use 'default' db. You can change this by creating custom database router.
Here, I am assuming that your directory structure for django project is:
./mainapp/
|--- mainapp/
| |--- settings.py
| |___ # .....
|
|--- app/
| |--- apps.py
| |--- dbrouters.py # [new file], we will be creating soon.
| |--- models.py
| |--- views.py
| |___ # .....
|
|--- manage.py
|___ # .....
Full example:
# app/models.py:
class Accounts (models.Model):
# .....
# app/dbrouters.py: # [new file]
from .models import Accounts
class AccountsDBRouter:
def db_for_read (self, model, **hints):
if (model == Accounts):
# your model name as in settings.py/DATABASES
return 'accounts'
return None
def db_for_write (self, model, **hints):
if (model == Accounts):
# your model name as in settings.py/DATABASES
return 'accounts'
return None
# mainapp/settings.py:
# .....
INSTALLED_APPS = [
'app.apps.AppConfig',
# .....
]
# .....
DATABASE_ROUTERS = (
'app.dbrouters.AccountsDBRouter',
)
DATABASES = {
# .....
'accounts' : {
# .....
},
}
# .....
Change the above code as per your requirement or specifications.
Then, do the following:
$ python3 manage.py makemigrations
$ python3 manage.py migrate --database=accounts
$ python3 manage.py migrate
Now, you should be able to use it without using('accounts') in code as follows:
# app/views.py:
# .....
from .models import Accounts
def someview (request):
accounts = Accounts.objects.all()
# See, in above line, you're not using:
# accounts = Accounts.objects.using('accounts').all()
# as your 'AccountsDBRouter' is already routing read and write
# db requests to 'accounts' database.
# Though you can still use "using('accounts')", as it will
# also provide same results.
def someotherview (request):
# You can even use the following:
account = Account(
email="<email>",
phone="<phone>",
# .....
)
account.save()
# Again, this will save directly in 'accounts'.
References:
Hope that answers you. :)
11
You have to route queries to the database too (emphasis is mine):
The easiest way to use multiple databases is to set up a database routing scheme. The default routing scheme ensures that objects remain ‘sticky’ to their original database (i.e., an object retrieved from the foo database will be saved on the same database).
The default routing scheme ensures that if a database isn’t specified, all queries fall back to the default database.
https://docs.djangoproject.com/en/2.1/topics/db/multi-db/#automatic-database-routing
NB: the db_table in your model's Meta is for the name of the database table, not the name of the database itself !-)
2
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