13. 如果添加多个数据到Django应用?¶
数据库配置相关的东西基本上在 settings.py
中被完成。所以,要给Django应用添加多个数据库,我们需要把他们添加到 DATABASES
的字典中。
DATABASE_ROUTERS = ['path.to.DemoRouter']
DATABASE_APPS_MAPPING = {'user_data': 'users_db',
'customer_data':'customers_db'}
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
},
'users_db': {
'NAME': 'user_data',
'ENGINE': 'django.db.backends.postgresql',
'USER': 'postgres_user',
'PASSWORD': 'password'
},
'customers_db': {
'NAME': 'customer_data',
'ENGINE': 'django.db.backends.mysql',
'USER': 'mysql_cust',
'PASSWORD': 'root'
}
}
对于多个数据库,我们最好聊聊 Database Router
。默认的路由方案如果一个数据库未指明,所有的查询都会返回到默认数据库。 Database Router
默认是 []
。
class DemoRouter:
"""
A router to control all database operations on models in the
user application.
"""
def db_for_read(self, model, **hints):
"""
Attempts to read user models go to users_db.
"""
if model._meta.app_label == 'user_data':
return 'users_db'
return None
def db_for_write(self, model, **hints):
"""
Attempts to write user models go to users_db.
"""
if model._meta.app_label == 'user_data':
return 'users_db'
return None
def allow_relation(self, obj1, obj2, **hints):
"""
Allow relations if a model in the user app is involved.
"""
if obj1._meta.app_label == 'user_data' or \
obj2._meta.app_label == 'user_data':
return True
return None
def allow_migrate(self, db, app_label, model_name=None, **hints):
"""
Make sure the auth app only appears in the 'users_db'
database.
"""
if app_label == 'user_data':
return db == 'users_db'
return None
各个模型将被修改为:
class User(models.Model):
username = models.Charfield(ax_length=100)
. . .
class Meta:
app_label = 'user_data'
class Customer(models.Model):
name = models.TextField(max_length=100)
. . .
class Meta:
app_label = 'customer_data'
使用多个数据库是的有用的命令:
$ ./manage.py migrate --database=users_db