Running manage.py makemigrations for multiple databases in django

Question

I'm trying to use multiple databases in my Django project i.e. MongoDB and MySQL.

# settings.py
DATABASES = {
    'default': {
        'NAME': 'sql_db',
        'ENGINE': 'django.db.backends.mysql',
        'USER': 'root',
        'PASSWORD': 'root'
    },
   'mongoproject': {
      'ENGINE' : 'djongo',
      'NAME': 'mongo_db'
   }
}

I create my model for eg

# App/models.py
class ForSQL(models.Model):
    Name = models.CharField(max_length=50)
    City = models.CharField(max_length=50)

I want to save it in MySQL. For that, I will run manage.py makemigrations and then manage.py migrate. It will save in MySQL.

But when I add one more table in models.py file like:

# App/models.py
class Mongo(models.Model):
    Name = models.CharField(max_length=50)
    City = models.CharField(max_length=50)

I want to save this table in MongoDB. If I run manage.py makemigrations and then run manage.py migrate --database=mongoproject, it saves 'Mongo' Table in MongoDB and also saves 'ForSQL' table in MongoDB because of previous migrations.

I need help in setting routers for differentiating migrations on each table. I looked for this solution but can't get them working.

You can make a database router: docs.djangoproject.com/en/3.0/topics/db/multi-db/#using-routers — willeM_ Van Onsem
– willeM_ Van Onsem, Commented Jul 18, 2020 at 12:54
I am using only one App and want to separate tables in different databases. But each time tables are created in each database. I've read the documentation and I think allow_migrate() could work. But unable to write it properly. — danish2694
– danish2694, Commented Jul 18, 2020 at 16:16

danish2694 · Accepted Answer · 2020-07-19 14:45:31Z

Here's how I solved my problem

# routers.py
import App.models
allmodels = dict([(name.lower(), cls) for name, cls in App.models.__dict__.items() if isinstance(cls, type)])

def allow_migrate(self, db, app_label, model_name = None, **hints):
    """ migrate to appropriate database per model """
    try:
        model = allmodels.get(model_name)
        return(model.params.db == db)
    except:
        pass

# App/models.py
class ForSQL(models.Model):
    class params:
        db = 'default'
    Name = models.CharField(max_length=50)
    City = models.CharField(max_length=50)

class Mongo(models.Model):
    class params:
        db = 'mongoproject'
    Name = models.CharField(max_length=50)
    City = models.CharField(max_length=50)

Then simply run commands manage.py makemigrations and manage.py migrate --database=default for default database (in my case MySQL) and manage.py migrate --database=mongoproject for MongoDB. It will save ForSQL table in MySQL and Mongo table in MongoDB.

This is what I exactly needed. Hope it will help someone.

Here it is what helped me https://stackoverflow.com/a/60453322/12134251

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