Django之连接多个数据库的相关配置

01-修改django默认的数据库

# settings.py

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'mysql01', #连接的数据库名
        'PORT': '3306',
        'HOST': 'localhost',
        'USER': 'root',
        'PASSWORD': '123456',
    }
}

# 修改项目同名目录下的__init__.py文件

import pymysql

pymysql.install_as_MySQLdb()

02-配置多数据库连接

# Django 要求default 数据库必须定义，但是如果不会用到，其参数字典可以保留为空。若要这样做，你必须为你的所有的应用的模型建立DATABASE_ROUTERS，包括正在使用的contrib 中的应用和第三方应用。

'default': {},

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'mysql01', #连接的数据库名
        'HOST': 'localhost',
        'PORT': '3306',
        'USER': 'root',
        'PASSWORD': '123456',
    }，
    'db02': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'db02', #连接的数据库名
        'HOST': 'localhost',
        'PORT': '3306',
        'USER': 'root',
        'PASSWORD': '123456',
    }
}

DATABASE_ROUTERS = ['项目名.database_router.DatabaseAppsRouter']
DATABASE_APPS_MAPPING = {
    'app01': 'default',
    'app02': 'db02',
}

03-实现数据库路由

# 下面我们需要在项目同名目录myproject/myproject下新建一个database_router.py来实现数据库路由

# database_router.py

from django.conf import settings

DATABASE_MAPPING = settings.DATABASE_APPS_MAPPING


class DatabaseAppsRouter(object):
    """
    A router to control all database operations on models for different
    databases.

    In case an app is not set in settings.DATABASE_APPS_MAPPING, the router
    will fallback to the `default` database.

    Settings example:

    DATABASE_APPS_MAPPING = {'app01': 'default', 'app02': 'db02'}
    """

    def db_for_read(self, model, **hints):
        """"Point all read operations to the specific database."""
        if model._meta.app_label in DATABASE_MAPPING:
            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

    def allow_syncdb(self, db, model):
        """Make sure that apps only appear in the related database."""

        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(model._meta.app_label) == db
        elif model._meta.app_label in DATABASE_MAPPING:
            return False
        return None

    def allow_migrate(self, db, app_label, model=None, **hints):
        """
        Make sure the auth app only appears in the 'auth_db'
        database.
        """
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(app_label) == db
        elif app_label in DATABASE_MAPPING:
            return False
        return None

    # for Django 1.4 - Django 1.6
    def allow_syncdb(self, db, model):
        """Make sure that apps only appear in the related database."""
 
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(model._meta.app_label) == db
        elif model._meta.app_label in DATABASE_MAPPING:
            return False
        return None
 
    # Django 1.7 - Django 1.11
    def allow_migrate(self, db, app_label, model_name=None, **hints):
        print(db, app_label, model_name, hints)
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(app_label) == db
        elif app_label in DATABASE_MAPPING:
            return False
        return None

04-为每个app的model分别指定所需要连接的数据库

# 编辑app01下的models.py:

class Book(models.Model): #该model使用default数据库
    name=models.CharField(max_length=32,primary_key=True,unique=True)
    

    def __str__(self):
        return self.name

    class Meta:
        #app_label = 'app01' #由于该model连接default数据库，所以在此无需指定
        ordering = ['name'] 
        db_table = 'book'  # 指定生成数据库的表名称

# 编辑app02下的models.py：

class Author(models.Model):
    name=models.CharField(max_length=32,primary_key=True,unique=True)
    age = models.CharFieid()

    def __str__(self):
        return self.name

    class Meta:
        app_label = 'app02'  #定义该model的app_label
        ordering = ['name'] 
        db_table = 'authoe'  # 指定生成数据库的表名称

05-同步数据库

# 同步default节点数据库，只运行不带 --database参数的命令，不对其他数据库进行同步

python manage.py makemigrations

python manage.py migrate

# 同步db02节点数据库：

python manage.py makemigrations

python manage.py migrate --database=db02