Let's say that we have a Django app that looks on a legacy database.
If someone make changes on some database tables from a db client as DBeaver for example and not through Django models, is there a way to identify these changes?
You can do in a terminal, inside your Django project directory : python manage.py inspectdb > models.py
You will have models related to your tables.
By default, inspectdb creates unmanaged models. That is, managed = False in the model’s Meta class tells Django not to manage each table’s creation, modification, and deletion.
If you do want to allow Django to manage the table’s lifecycle, you’ll need to change the managed option above to True (or remove it because True is its default value).
In my Django project, I would like two databases but only one model.
For example, an expert database and an exploit database. The router allows me to write in the exploit database or the expert database according to the users groups and permissions.
But how to duplicate the project model (described in model.py) in both bases?
You need to run migrate on each database. Use this switch to specify the database:
--database DATABASE Nominates a database to synchronize. Defaults to the
"default" database.
DATABASE in this case is the settings key that you are using in your settings.py field to configure each database.
I registered a new model in Django's admin interface but I can't see any permissions related to it that I can assign to users or groups.
Could it be related to the fact that my models come from a different database?
I fixed a very similar issue today where I couldn't assign Users permissions concerning tables that were created in multiple databases because those tables didn't appear in the list of "available permissions."
It appears that I accidentally migrated the model creation migrations to the default database before I correctly used the --database DATABASE flag with manage.py migrate. So I had the same table names in both the default and auxiliary databases. I dropped the tables in the default database, leaving only the tables in the auxiliary database, and then the tables appeared in the permissions list.
In a django app, I have two postgresql databases connected through settings.py: one is default and other is AppDb. AppDb is placed on a remote machine.
I want to query from a 'Courses' model from AppDb using 'using()' and 'Courses' model is not available in default database.
So my query goes like this:
courseInfo = Courses.objects.using('AppDb').filter(cuser_id = 12)
But I am getting NameError for 'Courses'
Can I have a solution for such queries without using routers
If you have an existing database, you still need to create an app and models for that database in order to use the ORM.
To help you create the model classes, you can use the inspectdb management command which will try to guess the models from an existing database and create the models.py for you. Its not perfect, but it will save you some time.
You will still have to make sure the models have a primary key and are written in the correct order (so that foreign keys will work correctly).
I'm taking EdX classes that use Ruby on Rails and python. That has given me courage to try and install and learn Django using Apach, mod_wsgi, and PostgreSQL. Following the detailed installation instructions, I first installed Apache, then mod_wsgi, and then PostgreSQL. I installed each from source and went through a little bit of tutorial with each and made sure they were properly installed. I've got a postgres user setup to run the PostgreSQL server and I was able to create a user "role" for myself as well as an admin role that my role inherits from that can create a database etc. I tried out some SQL in psql following a tutorial to make tables etc. I know how to grant privileges for a given role.
So anyway, I'm pretty close to the step where I would actually install Django from source, but I'm not sure how to follow this advice from the installation instructions:
If you plan to use Django's manage.py syncdb command to automatically create database tables for your models, you'll need to ensure that Django has permission to create and alter tables in the database you're using; if you plan to manually create the tables, you can simply grant Django SELECT, INSERT, UPDATE and DELETE permissions.
Maybe after I follow the steps to actually install Django and go through some tutorials, I'll understand exactly what needs to be setup in PostgreSQL to grant Django those permissions, but if I follow the installation instructions in order, it would seem to be saying I should setup those permissions now before installing Django. If I can get someone to tell me how to do it here before I do the install of Django, I'd appreciate it.
In the settings.py file of a django project, there is a snippet that says something like this:
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql_psycopg2',
'NAME': 'myproj_db',
'USER': 'myproj_user',
'PASSWORD': '123',
'HOST': '',
'PORT': '',
},
}
What this does is that it tells Django what user (postgres user in this case) and database is used in conjunction with your django project.
Normally, you will need to create this myproj_user together with the myproj_db.
When you create this user, you can choose to give it permissions like so:
CREATE USER myproj_user WITH PASSWORD '123' SUPERUSER CREATEDB CREATEROLE LOGIN;
This creates the myproj_user with superuser, createdbm createrole, login permissions allowed to the user.
And then the database like so:
CREATE DATABASE myproj_db WITH OWNER myproj_user TEMPLATE=template1 ENCODING='utf-8';
You say that you know how to grant privileges for a given role, which is what you need to do for Django before installing it (running syncdb).
This is part of setting up your database for use with Django – a step you take before creating each Django project. Each Django project corresponds to a site that you build with Django and is completely separate from another Django project. To each project belongs a database.* You can install Django the framework before you setup your database, because Django the framework doesn't do anything on its own.
Either you give Django permissions to create tables for you, in which case it can create tables for you (using manage.py syncdb). Or, you use manage.py sqlall <app> to get SQL that you run yourself to create the tables needed (which might be nice if you're paranoid about security).
To grant all permissions to a user for a specific database (option 1) in Postgres, use the command (from psql):
GRANT ALL PRIVILEGES ON DATABASE <db-name> TO <username>;
* Technically, they can share a database by simply configuring them to use the same one.
Django uses ORM (Object Relational Mapper). What that means is that you do not directly deal with database tables for querying things however you deal with certain classes which then deal with the database. This is very useful and much more user-friendly then doing manually SQL. Consider the following example:
SELECT * FROM foo WHERE field="value"
vs
Foo.objects.filter(field='value')
In ORM, you describe the tables you have by making certain classes (in Django we call them models) and those models correspond to tables in the db, and their fields correspond to the columns in the db table. The following are very similar:
CREATE TABLE foo (
title varchar(50),
description text,
likes integer
);
and
class Foo(models.Model):
title = models.CharField(max_length=50)
description = models.TextField()
likes = models.IntegerField()
However it is waste of time for you as a developer to construct the SQL statements for creating tables, and describing those tables in Python as models. Not to do that, Django allows you once you define all your models, to create db tables for you. That is the purpose of the syncdb command. It takes all the installed apps and models within them and creates tables within your database for them. However as you already mentioned in your question, databases have roles and those roles have permissions. For example, one of the permissions is CREATE as described here. So what Django documentation is saying is for you to grand all necessary permission to a role which Django will use to interact with the db for Django to be able to create necessary db tables it needs as well as possibly modify them later.