Develop Reference

Can't apply migrations in Django SQLlite memory database

I'm writing some tests, and I want to be able to run django server with my test settings (that's why I'm using in-memory database).
It seems to be working, no errors reported when running. But migrations are not applied - I can't perform any action on the database, because model tables do not exist.
When I run python manage.py migrate, all my migrations get applied (I see these Applying migrations... OK messages), but it has no effect. When I run python manage.py showmigrations, none of the migrations are applied (I see [ ] 0001_initial etc., without the X).
When I go to django shell, I can't perform any action, because table does not exist. Any idea what might be the reason? It works fine with normal, postgres database.
My settings:
DEBUG = True
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': ':memory:',
'TEST_NAME': ':memory:',
},
}
CACHES = {
'default': {
'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
'LOCATION': ''
}
}

How to make two django projects share the same database

I need to make two separate Django projects share the same database. In project_1 I have models creating objects that I need to use in project_2 (mostly images).
The tree structure of project_1_2 is:
project_1/
manage.py
settings.py
project_1_app1/
...
...
project_2/
manage.py
settings.py
project_2_app1/
...
...
Which is the best approach?
EDIT: I'm using sqlite3 in my development environment.
I'd like to keep my two django projects as stand-alone projects (so that both can be upgraded safely from their respective repositories).
# in project_1/settings.py
import os
PROJECT_ROOT = os.path.abspath(os.path.dirname(__file__))
..
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(PROJECT_ROOT, 'development.db'),
},
}
...
# in project_2/settings.py
import os
PROJECT_ROOT = os.path.abspath(os.path.dirname(__file__))
..
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(PROJECT_ROOT, 'development.db'),
},
}
...
In this way, each project has its own development.db (the one that I need to be shared):
project_1/development.db
project_2/development.db
but I guess I need to do something more to make it shared (and unique).
The best for me would be to keep the development.db at project_1/ path and thus set the project_2/settings.py DATABASES to point to project_1/development.db.

You can simply define the same database in DATABASES in your settings.py. So, if your database is PostgreSQL, you could do something like this:
# in project_1/settings.py
DATABASES = {
'default': {
'NAME': 'common_db',
'ENGINE': 'django.db.backends.postgresql',
'USER': 'project_1_user',
'PASSWORD': 'strong_password_1'
},
}
# in project_2/settings.py
DATABASES = {
'default': {
'NAME': 'common_db',
'ENGINE': 'django.db.backends.postgresql',
'USER': 'project_2_user',
'PASSWORD': 'strong_password_2'
},
}
Note that both database users (project_1_user and project_2_user) should have the appropriate privileges on the database you wish to use. Or you could instead use the same user for both projects.
If you want to have more than just one database per project, you should take a look at the docs for multiple databases.
On another matter, since you share data, I guess you share functionalities as well. So for example, if project_1_app1 and project_2_app1 do same (or similar) things, it seems they could instead be a single reusable app.
Edit
Since you use sqlite3, you should ensure the path you use is the same. So, assuming that project_1 and project_2 are siblings, like so:
projects
project_1
settings.py
...
project_2
settings.py
...
you should try this:
# project_1/settings.py
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(PROJECT_ROOT, 'development.db'),
},
}
# project_2/settings.py
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(
os.path.dirname(os.path.dirname(PROJECT_ROOT)),
'project_1',
'development.db'
),
},
}
This would give the structure you ask for. Note however that the projects are not both "standalone". project_2 is clearly dependent on project_1's database.
In any case, perhaps, you should also take a look at the os.path module for more info.

You just need to declare in your model in class meta the attribute db_table with a name diferent the name of app + model (Which are automatically generated by Django) the twice projects need the same models. before the run makemigrations and migrate.
class MyModel(models.Model):
class Meta:
db_table = 'MyModel'

put installed app model in selected database

I have installed app named registration-redux, and I would like to store user data (and some other minor things) in a sqlite database called default. However, the data structures get added automatically to other databases, which is redundant.
Normally, I go to models.py and put in a desired model a label:
class some_model(models.Model):
name = models.CharField(max_length=20, primary_key=True)
class Meta:
app_label = 'default'
And in settings.py I select which models go to which database:
DATABASE_APPS_MAPPING = {'market_data': 'market_data',
'registration': 'default'} # this doesn't work
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
},
'market_data': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'market_data.sqlite3'),
}
}
Now, when I migrate market_data database, redundant structures like auth_user, auth_group, etc. get added. How can I omit them?

For Django 1.7
Create file routers.py, and in this file write:
class Market_data_router(object):
def allow_migrate(self, db, model):
if db == 'market_data':
if model.__name__ != 'Market_data':
return False
return None
In settings.py write:
DATABASE_ROUTERS = ['routers.Market_data_router']
At the end, create ,,clear" database:
./manage.py migrate --database=market_data

How to read table data from non-default database in Django?

My django project uses 2 databases, 1 existing database and another one which I am creating through my project using Models. I have defined db's in settings.py as below :
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
},
'music': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'myMusicDb.sqlite3'),
}
}
I generated model data using inspectdb command and everything works fine if I remove the default db from settings.py and make the 'music' db the default db. My query is how to keep both db in settings.py and to work with both DataBases ? Is there any way to tell django to use specific database from settings.py ?

I found the answer after reading https://docs.djangoproject.com/en/1.7/topics/db/multi-db/.
We can either use routers or we can make use of using keyword in query such as -
Album.objects.using('music').all()
Thought to post it, may be it could help someone.

Configure Django with MS SQL Server database

I'm setting up a Django application and I want to use SQL Server 2012 for my database.
To configure my website I'm following this section of the official Django documentation.
In the section Database setup I found instructions for changing RDBMS.
And in settings.py file I found these instructions for setting up Django with SQlite.
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
}
}
How I can change this configuration to use SQL Server 2012 instead?

Looks like you'll need django-mssql which requires django 1.4 or below:
http://django-mssql.readthedocs.org/en/latest/
It has a pip package: https://pypi.python.org/pypi/django-mssql
Then include in your settings.py:
DATABASES = {
'default': {
'NAME': 'my_database',
'ENGINE': 'sqlserver_ado',
'HOST': 'dbserver\\ss2008',
'USER': '',
'PASSWORD': '',
}
}