在django裏使用多個數據庫

轉載自：http://blog.csdn.net/feng88724/article/details/7177957

1.2之後，  django支持在項目中使用多個DB. 那麼到底如何使用呢？

1. 修改 settings.py

01DATABASES = {

02    'default': {

03        'NAME': 'app_data',

04        'ENGINE': 'django.db.backends.postgresql_psycopg2',

05        'USER': 'postgres_user',

06        'PASSWORD': 's3krit'

07    },

08    'users': {

09        'NAME': 'user_data',

10        'ENGINE': 'django.db.backends.mysql',

11        'USER': 'mysql_user',

12        'PASSWORD': 'priv4te'

13    }

14}

15 

16DATABASE_ROUTERS = ['path.to.MyAppRouter']

2. 實現自己的DB routers，這裏決定了每個程序使用的是哪個DB。

01class MyAppRouter(object):

02    """A router to control all database operations on models in

03    the myapp application"""

04 

05    def db_for_read(self, model, **hints):

06        "Point all operations on myapp models to 'other'"

07        if model._meta.app_label == 'myapp':

08            return 'other'

09        return None

10 

11    def db_for_write(self, model, **hints):

12        "Point all operations on myapp models to 'other'"

13        if model._meta.app_label == 'myapp':

14            return 'other'

15        return None

16 

17    def allow_relation(self, obj1, obj2, **hints):

18        "Allow any relation if a model in myapp is involved"

19        if obj1._meta.app_label == 'myapp' or obj2._meta.app_label == 'myapp':

20            return True

21        return None

22 

23    def allow_syncdb(self, db, model):

24        "Make sure the myapp app only appears on the 'other' db"

25        if db == 'other':

26            return model._meta.app_label == 'myapp'

27        elif model._meta.app_label == 'myapp':

28            return False

29        return None

同步數據庫的時候，默認會同步到Default數據庫，當然也可以通過 --database 來指定同步哪一個， 如下：

<tt class="xref std std-djadminopt docutils literal" style="text-decoration: none; white-space: nowrap; color: rgb(35, 79, 50); margin-left: 0px; margin-right: 0px; border-bottom-width: 1px; border-bottom-color: rgb(35, 79, 50); border-bottom-style: dotted; ">$ ./manage.py syncdb
$ ./manage.py syncdb --database=users</tt>

那麼程序中如何來選擇呢？

比如，下面的代碼將選擇default數據庫

<span style="font-family:monospace;color:#234f32;">>>> # This will run on the 'default' database.
>>> Author.objects.all()

>>> # So will this.
>>> Author.objects.using('default').all()</span>

但是下面的代碼將選擇other數據庫

<span style="font-family:monospace;color:#234f32;">>>> # This will run on the 'other' database.
>>> Author.objects.using('other').all()</span>

上面是查詢的情況，保存的使用也一樣，也是通過using來指定，如下:

<span style="font-family:monospace;color:#234f32;">>>> my_object.save(using='legacy_users')</span>

刪除的時候

<span style="font-family:monospace;color:#234f32;">>>> u = User.objects.using('legacy_users').get(username='fred')
>>> u.delete() # will delete from the `legacy_users` database</span>

更多內容請至此查看： https://docs.djangoproject.com/en/1.3/topics/db/multi-db/