django中使用多个数据库，跨库查询

DATABASES = {
     ‘default‘: {
        # ‘ENGINE‘: ‘django.db.backends.mysql‘,
        ‘ENGINE‘: ‘common_framework.utils.mysql‘,
        ‘NAME‘: ‘choice‘,
        ‘USER‘: ‘ad_user‘,
        ‘PASSWORD‘: ‘ad_pass‘,
        ‘HOST‘: ‘127.0.0.1‘,
        ‘PORT‘: ‘3306‘,
        ‘SIZE‘: ‘10‘,
    },

    ‘platform‘: {
        # ‘ENGINE‘: ‘django.db.backends.mysql‘,
        ‘ENGINE‘: ‘common_framework.utils.mysql‘,
        ‘NAME‘: ‘test‘,
        ‘USER‘: ‘ad_user‘,
        ‘PASSWORD‘: ‘ad_pass‘,
        ‘HOST‘: ‘192.168.10.179‘,
        ‘PORT‘: ‘3306‘,
        ‘SIZE‘: ‘10‘,
    }
}

# -*- coding: utf-8 -*-
from django.conf import settings
from event.models import Event
DATABASE_MAPPING = settings.DATABASE_APPS_MAPPING
class DataBaseAppsRouter(object):

    def db_for_read(self, model, **hints):
        """"Point all read operations to the specific database."""
        if model._meta.app_label in DATABASE_MAPPING:
            if model == Event:
                return "default"
            else:
                return DATABASE_MAPPING[model._meta.app_label]
        return None
    def db_for_write(self, model, **hints):
        """Point all write operations to the specific database."""
        if model._meta.app_label in DATABASE_MAPPING:
            return DATABASE_MAPPING[model._meta.app_label]
        return None
    # def allow_relation(self, obj1, obj2, **hints):
    #     """Allow any relation between apps that use the same database."""
    #     db_obj1 = DATABASE_MAPPING.get(obj1._meta.app_label)
    #     db_obj2 = DATABASE_MAPPING.get(obj2._meta.app_label)
    #     if db_obj1 and db_obj2:
    #         if db_obj1 == db_obj2:
    #             return True
    #         else:
    #             return False
    #     return None

EventUserAnswer.objects.using("platform").filter(user=user, team=request.user.team, status=1).first():