I want to generate SQL code and take from that code, generating a Django model to avoid errors.
They will say that you first create the model and run the syncdb or migrate but my case is unlike the database is already created and I now want the model
Run this command to auto-generate models from an already existing database. But first make sure you've properly linked database to django app .
python manage.py inspectdb > models.py
Do check models.py file and make some changes if you something isn't rendered correctly.
For inspectdb approach, read this: https://docs.djangoproject.com/en/1.8/howto/legacy-databases/
Alternatively, you can write all the models by yourself and set managed = False. No database table creation of deletion will be executed by Django on this model. But it is somewhat complicated and puts some limits on model relationships.
For managed=False approach, read this: https://docs.djangoproject.com/en/1.8/ref/models/options/#managed
Related
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).
Background
I've got a Django app that I want to test. The Django app relies on database tables that were created by a different, non-Django app, but in the same database. Every time I try to run a test I get the following error:
django.db.utils.ProgrammingError: relation "mytable" does not exist
I'm thinking that this error is caused by the fact that the table was created manually and there are no migrations.
Question
Is there a way I can tell Django to build migration files based off of a database table that already exists?
There is a tool called inspectdb in Django for this exact scenario.
This should do the trick:
python manage.py inspectdb > models.py
For reference:
https://docs.djangoproject.com/en/3.2/howto/legacy-databases/
I have a Django app with a model MyModel and some field my_field. My PostgreSQL database already has a field of that name under the mymodel table, since it was added manually in the past. When I make migrations, Django generates an AddField operation, which is in conflict. Currently I manually edit every generated migration to remove the conflict.
Is there a way to tell Django that the field already exists?
Unfortunately this is a live product, so I cannot lose any data.
Generate the migration that adds the field and then run python manage.py migrate <app_name> <migration_name> --fake to mark the migration as applied without actually running it
Thank you Iain Shelvington.
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.
As I want to customize Django user model, I migrated from default user model to my own custom user model. Since my Django project has been working since a long time ago, I need to keep the existing user data.
I was thinking to move them manually, but Django default user model's passwords are hidden. How can I safely move existing user data to my custom user model?
Moving to CustomUser is no easy task in Django. If you want to keep the existing data, then as per ticket #25313, you need to do the following steps:
Create a custom user model identical to auth.User, call it User (so many-to-many tables keep the same name) and set db_table='auth_user' (so it uses the same table).
Throw away all your migrations from all the apps(except for __init__.py file inside the migrations folder).
Recreate a fresh set of migrations(using python manage.py makemigrations).
Make a backup of your database.
Delete all entries from django_migrations table from DB.
Fake-apply the new set of migrations(using python manage.py migrate --fake).
Optional: Set db_table="your_custom_table" or remove it altogether.
Make other changes to the custom model, generate migrations, apply them.
You can dump your existing model data with dumpdata command and also able to reload those data to that model or your changed custom model with loaddata command. Here is a good example how you can able to do that. link