default_database_router.py

from django.conf import settings


class DefaultDatabaseRouter(object):
    def db_for_read(self, model, **hints):
        """
        This is the fall through. If the table isn't found in mk_web_core, it must be here.
        """
        if model._meta.app_label in ['accounts', 'materials',]:
            return 'mk_web_core'
        else:
            return 'default'

    def db_for_write(self, model, **hints):
        """
        This is the fall through. All writes should be directed here.
        """
        if model._meta.app_label in ['accounts', 'materials',]:
            if settings.TESTING:
                return 'mk_web_core'
            else:
                raise Exception('Attempt to write to mk_web_core from mk_ai when settings.TESTING not true!')
        else:
            return 'default'

    def allow_relation(self, obj1, obj2, **hints):
        """
        Relations between objects are allowed if both objects are in the same pool.
        """
        return obj1._state.db == obj2._state.db

    def allow_migrate(self, db, app_label, model=None, **hints):
        """
        Write to test_mk_web_core when we are running unit tests.

        The check for model is because the contenttypes.0002_remove_content_type_name
        migration fails with message: AttributeError: 'NoneType' object has no attribute '_meta'
        """
        if app_label in ['accounts', 'materials',]:
            if db == 'mk_web_core' and settings.TESTING:
                return True
            else:
                return False
        else:
            # Shortcut, we do import into default (mk_ai) but not into mk_web_core
            return db == 'default'