Django - how to specify a database for a model?

Question

Is there a way to specify that a model (or app, even) should only ever use one particular database?

I am working with a legacy database that I don\'t want to change.

Answer 1

I found that you can route models pretty simply with this manager:

class SecondDbManager(models.Manager):
    def get_queryset(self):
        qs = super().get_queryset()

        # if `use_db` is set on model use that for choosing the DB
        if hasattr(self.model, 'use_db'):
            qs = qs.using(self.model.use_db)

        return qs

Just add use_db='databasename' and this manager to your model and it works.

Or to further simplify it I created a base model for it:

class SecondDbBase(models.Model):
    use_db = 'my_second_db'
    objects = SecondDbManager()

    class Meta:
        abstract = True

And with this all you need to do is extend it like so. Instead of:

class Customer(models.Model):

Just do this and it works:

class Customer(SecondDbBase):

PS. I'm not sure if it's a good practice or the best solution but it works and routing to other databases is a breeze :)

PPS. I've only ever used these for only reading and writing tables that are not managed by Django(managed = False) so if you need to create migrations for them, I'm not sure if it works or not. Might still need to use DATABASE_ROUTERS for that.