Django：同一个app支持多个数据库

我以我个人的Mynote工程说明，目的是要在backend这个app里面设置不同的model对应daysn和bear两个数据库进行操作

现在我们先简单对一个完全新建的django工程配置一个自动在mysql生成表的这么一个东西，

配置setting

然后随便写个model

然后

E:\大数据\DjangoMyNote\Mynote>python manage.py makemigrations backend
Migrations for 'backend':
  backend\migrations\0001_initial.py
    - Create model test

E:\大数据\DjangoMyNote\Mynote>python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, backend, contenttypes, sessions
Running migrations:
  Applying backend.0001_initial... OK

然后就创建了一个表，好，这是前提。ps，其他表先建了

好，从这里开始记录一个完整的一个app对应多个数据库的过程，综合了n篇博客妈的没有一篇靠谱

首先我们建立一个空的app，假设叫another

那么我们在我们的主工程的setting肯定要注册进去，顺便配置一下我们的数据库连接

DATABASES = {
    #系统默认加载的数据库daysn，于是这里的数据库连接名为default
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME':'daysn',
        'USER':'root',
        "PASSWORD":'',
        "HOST":"*.*.*.*",
        "PORT":"",
        "CONN_MAX_AGE":*,
    },

 #系统加载的数据库第二个bear，于是这里的数据库连接名为default

'default2': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME':'bear',
        'USER':'root',
        "PASSWORD":'',
        "HOST":"*。*。*。*",
        "PORT":"",
        "CONN_MAX_AGE":*,
    },
}
#待会我们在主工程的目录下新建一个DatabaseAppRouter文件，里面定义了一个DatabaseAppsRouter的class
DATABASE_ROUTERS = ['Mynote.DatabaseAppRouter.DatabaseAppsRouter']
#两个应用对应不同的数据库
DATABASE_APPS_MAPPING = {
        'backend': 'default',
        'another': 'default2',
}

好，现在我们新建一个路由就像上面说的

然后下面这段代码完全copy

# -*- coding: utf- -*-
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 = {'app1': 'db1', 'app2': 'db2'}
    """

    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

    # 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):
        """
        Make sure that apps only appear in the related database.
        根据app_label的值只在相应的数据库中创建一个表，如果删除该def或
        不指定过滤条件，则一个Model会在每个数据库里都创建一个表。
        """
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(app_label) == db
        elif app_label in DATABASE_MAPPING:
            return False
        return None

然后我们可以去写我们的类了，因为我们的目的是要在backend这个app里面设置不同的model同时对应daysn和bear这两个数据库

那么测试如下，在backend的model.py里面加入这些玩意儿

from django.db import models

# Create your models here.

class test(models.Model):
    test_id = models.IntegerField()
    test_a_id = models.IntegerField()

class mt(models.Model):
    test_id = models.IntegerField()
    test_a_id = models.IntegerField()

class another(models.Model):
    test_id = models.IntegerField()
    test_a_id = models.IntegerField()
    class Meta:
        app_label = 'another'

class dsasdas(models.Model):
    test_id = models.IntegerField()
    test_a_id = models.IntegerField()
    class Meta:
        app_label = 'another'

同步数据库要使用的是

python manage.py makemigrations

然后同步default
python manage.py migrate 

同步非default
python manage.py migrate --database==default2

这样才会同步完两个数据库

好的，一个app连接多个数据库表演完毕。

ps：我认为应该有其他方式啊。。不应该要通过新建一个没怎么用的空app  another来搞，哪路大神知道的话希望能救下小弟。