How to Use Database Router for Multiple Databases

How to Use Database Router for Multiple Databases

August 21, 2022
database

Using multiple database in the Django project you may face with situation when you need apply migrations for some app or model just to the some databse instead all of defined databases, or you need to perform read/write actions for models of the some application only for specific database instead specifying .using(db) every time.

For this purpose use need define and enable database router.

Define database router #

This example demonstrates how to restrict read/write/migration operations of the “example_app” models to the “database2” only.

app/dbrouter.py # 

class ExampleAppDatabaseRouter(object):

    def db_for_read(self, model, **hints):
        if model._meta.app_label == 'example_app':
            return 'database2'
        return None

    def db_for_write(self, model, **hints):
        if model._meta.app_label == 'example_app':
            return 'database2'
        return None
    
    def allow_migrate(self, db, app_label, model_name=None, **hints):
        if app_label == 'example_app':
            return db == 'database2'
        elif db == 'database2':
            return False

settings.py #

Specify list of all your defined routers in the settings.py file.

DATABASE_ROUTERS = [
    'app.dbrouter.ExampleAppDatabaseRouter', 
]

Restrict defined models to the single database # 

class ExampleAppDatabaseRouter(object):
    
    def allow_migrate(self, db, app_label, model_name=None, **hints):
        if db == 'database2':
            if model_name not in ['comments', 'likes']:
                return False

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