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).
Related
I have a table containing a list of subclasses of a certain class in my django app.
How can I make django require a data migration when this table is edited ?
Is there some exception I can raise if django is started and one of these classes isn't in the table ?
I'd also like to be able to hook into makemigrations so I can generate the correct data migration if possible.
I am working on already existing data on relational database. Now question is that how to build models and how to update the tables with new data coming from user (technically django forms)?
Django natively supports creating models for and working with existing data. From the documentation:
Integrating Django with a legacy database
Django will still need to create several of its own tables, but will adapt to use your existing tables. From the doc, you can auto-create models like this:
python manage.py inspectdb > models.py
You'll need to determine whether you want to manage updates to the table structure, but that's getting into details that will be specific to your project.
I spin up a django project. Afterwards, i didn't write models.py but instead I created a database from MySQL command line(independent from django) and created three tables with required columns. Finally i connected my django app with that database successfully. I applied migrations. But now i am confused do i need to write models.py with every field name as in column?
I remember implementing a basic project in which i did write models.py and created database using "python manage.py shell" and then put values using
"from polls.models import Choice, Question"? How do i put data now initially and then using python on some action from UI?
Do i need models.py even for ready made mysql databases?
You do not need to construct models. Some (small) webservers are even completely stateless, and thus do not use a database. But a large part of how Django can help you is based on models.
You can write your own queries, forms, etc. But often by using a ModelForm, Django can for example remove a large amount of boilerplate code. It will make it furthermore less likely that there are mistakes in your code. So although not strictly necessary, the models are usually a keystone in how Django can help you.
You can use the inspectdb [Django-doc] command to inspect the database, and let Django "sketch" the models for you. Usually you will have still some work. Since Django can, for example, not derive that a field is an EmailField, since both a CharField and EmailField look exactly the same at the database side.
You do not need to use inspectdb however. You can construct your own models. If you create your own models, but these exist already at the database side, you might want to set managed = False [Django-doc] in the Meta of your model, to prevent Django from constructing migrations.
We have a Django application that has been in production since Django 1.1. Over the years, we've manually added bells and whistles to the production PostgreSQL db that weren't at the time overtly supported by Django's db automation, especially in the form of custom indexes.
Django's come a long way since 1.1, and now w/ 1.10 I'm pretty sure the migration framework supports all the custom features we've added manually. Is there any automated tool which will compare a database to the models, and generate migrations to bring the models up to date with the db?
This is built into django, you can just run inspectdb
manage.py inspectdb
Introspects the database tables in the database pointed-to by the NAME setting and outputs a Django model module (a models.py file) to standard output. You may choose what tables to inspect by passing their names as arguments.
Use this if you have a legacy database with which you’d like to use Django. The script will inspect the database and create a model for each table within it.
I have defined two databases in my settings.py with default, cas.
In my accounts application models.py I have created two clases
UserProfile and Users.
I want to tie UserProfile table to default and Users to cas db setting:
so for e.g. when I do a syncdb using the following command
python manage.py syncdb --database=cas
it should create only the users table in CAS and not the UserProfile table too.
Is there a way I can achieve this?
Take a look at the Database routing features of Django 1.2. You'll likely find what you need:
http://docs.djangoproject.com/en/dev/topics/db/multi-db/#automatic-database-routing