Django multiple databases ... all models are created in second db despite router, is my router not good?

Question

Django 2.2.18

I want to split the models of one app to a second database. The relevant app is named "dear_zoho_analytics", which I assume is the 'app_label'. The original database is "default".

I have only one dbrouter, and it has code like this:

class DbRouter(object):
    
    route_app_labels = ["dear_zoho_analytics", ]
    def db_for_read(self, model, **hints):
        .
        .
        .


    def allow_migrate(self, db, app_label, model_name=None, **hints):
      
        if app_label in self.route_app_labels:
            return db == "dear_analytics"
        return None

when I do this:

python3 ./manage.py migrate --database=dear_analytics

I get the tables of every app created in the new database.

python3 ./manage.py migrate dear_zoho_analytics --database=dear_analytics does what I want. However, this sort of implies that my allow migrate is not working because it appears to do nothing useful.

Abdul Aziz Barkat · Accepted Answer · 2021-02-07 12:00:04Z

1

What you want to do is to return False if the app_label is not "dear_zoho_analytics" when the db is "dear_analytics":

def allow_migrate(self, db, app_label, model_name=None, **hints):
    if app_label in self.route_app_labels:
        if db != "dear_analytics":
            return False
        return True
    elif db == "dear_analytics":
        return False
    return None

I have assumed you want this apps tables only in the "dear_analytics" db. Otherwise you may have to modify conditions a little.

answered Feb 7, 2021 at 12:00

Abdul Aziz Barkat

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iklinac · Accepted Answer · 2021-02-07 13:00:28Z

1

Your routing ensures that dear_zoho_analytics app is routed to dear_analytics, for rest of apps they are routed to all databases

simply adding additional condition would ensure other apps not being migrated to second database

def allow_migrate(self, db, app_label, model_name=None, **hints):
    if app_label in self.route_app_labels:
        return db ==  "dear_analytics"
    else:
        return db != "dear_analytics"

edited Feb 7, 2021 at 13:00

answered Feb 7, 2021 at 12:46

iklinac

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