Django使用多數據庫的方法

DATABASES = {
 'default': {
 'NAME': 'app_data',
 'ENGINE': 'django.db.backends.postgresql',
 'USER': 'postgres_user',
 'PASSWORD': 's3krit'
 },
 'users': {
 'NAME': 'user_data',
 'ENGINE': 'django.db.backends.mysql',
 'USER': 'mysql_user',
 'PASSWORD': 'priv4te'
 }
}

DATABASES = {
 'default': {},
 'users': {
 'NAME': 'user_data',
 'ENGINE': 'django.db.backends.mysql',
 'USER': 'mysql_user',
 'PASSWORD': 'superS3cret'
 },
 'customers': {
 'NAME': 'customer_data',
 'ENGINE': 'django.db.backends.mysql',
 'USER': 'mysql_cust',
 'PASSWORD': 'veryPriv@ate'
 }
}

class MyUser(models.Model):
 ...
 class Meta:
 app_label = 'users'

DATABASES = {
 'default': {},
 'auth_db': {
 'NAME': 'auth_db',
 'ENGINE': 'django.db.backends.mysql',
 'USER': 'mysql_user',
 'PASSWORD': 'swordfish',
 },
 'primary': {
 'NAME': 'primary',
 'ENGINE': 'django.db.backends.mysql',
 'USER': 'mysql_user',
 'PASSWORD': 'spam',
 },
 'replica1': {
 'NAME': 'replica1',
 'ENGINE': 'django.db.backends.mysql',
 'USER': 'mysql_user',
 'PASSWORD': 'eggs',
 },
 'replica2': {
 'NAME': 'replica2',
 'ENGINE': 'django.db.backends.mysql',
 'USER': 'mysql_user',
 'PASSWORD': 'bacon',
 },
}

class AuthRouter(object):
 """
 A router to control all database operations on models in the
 auth application.
 """
 def db_for_read(self, model, **hints):
 """
 Attempts to read auth models go to auth_db.
 """
 if model._meta.app_label == 'auth':
 return 'auth_db'
 return None
 def db_for_write(self, model, **hints):
 """
 Attempts to write auth models go to auth_db.
 """
 if model._meta.app_label == 'auth':
 return 'auth_db'
 return None
 def allow_relation(self, obj1, obj2, **hints):
 """
 Allow relations if a model in the auth app is involved.
 """
 if obj1._meta.app_label == 'auth' or \
 obj2._meta.app_label == 'auth':
 return True
 return None
 def allow_migrate(self, db, app_label, model_name=None, **hints):
 """
 Make sure the auth app only appears in the 'auth_db'
 database.
 """
 if app_label == 'auth':
 return db == 'auth_db'
 return None

import random
class PrimaryReplicaRouter(object):
 def db_for_read(self, model, **hints):
 """
 Reads go to a randomly-chosen replica.
 """
 return random.choice(['replica1', 'replica2'])
 def db_for_write(self, model, **hints):
 """
 Writes always go to primary.
 """
 return 'primary'
 def allow_relation(self, obj1, obj2, **hints):
 """
 Relations between objects are allowed if both objects are
 in the primary/replica pool.
 """
 db_list = ('primary', 'replica1', 'replica2')
 if obj1._state.db in db_list and obj2._state.db in db_list:
 return True
 return None
 def allow_migrate(self, db, app_label, model_name=None, **hints):
 """
 All non-auth models end up in this pool.
 """
 return True

DATABASE_ROUTERS = ['path.to.AuthRouter', 'path.to.PrimaryReplicaRouter']

$ ./manage.py migrate
$ ./manage.py migrate --database=users

>>> # This will run on the 'default' database.
>>> Author.objects.all()
>>> # So will this.
>>> Author.objects.using('default').all() 
>>> # This will run on the 'other' database.
>>> Author.objects.using('other').all()

>>> my_object.save(using='legacy_users')

>>> p = Person(name='Fred')
>>> p.save(using='first') # (statement 1)
>>> p.save(using='second') # (statement 2)

>>> p = Person(name='Fred')
>>> p.save(using='first')
>>> p.pk = None # Clear the primary key.
>>> p.save(using='second') # Write a completely new object.

>>> p = Person(name='Fred')
>>> p.save(using='first')
>>> p.save(using='second', force_insert=True)

>>> u = User.objects.using('legacy_users').get(username='fred')
>>> u.delete() # will delete from the `legacy_users` database

>>> user_obj.save(using='new_users')
>>> user_obj.delete(using='legacy_users')