Django 多數(shù)據(jù)庫聯(lián)用 -- 同一個APP的models里不同class用不同數(shù)據(jù)庫

很多網(wǎng)站有多數(shù)據(jù)庫聯(lián)用的文章，如自強學堂http://code.ziqiangxuetang.com/django/django-multi-database.html
大都只講解如何讓不同的app對應(yīng)不同的數(shù)據(jù)庫，而沒有談到如何讓同一個app里的不同class對應(yīng)不同的數(shù)據(jù)庫。
經(jīng)過N多次試驗，歷經(jīng)好幾天時間，終于找出如下的簡便易行的途徑，而不需要自己造輪子，現(xiàn)總結(jié)如下：

方式一：通過數(shù)據(jù)庫路由自動分發(fā)Model，無需手動using

settings配置如下：

1、增加了DATABASE_ROUTERS，用于指定路由路徑
2、增加了DATABASE_APPS_MAPPING，指定app_label對應(yīng)的數(shù)據(jù)庫

DBNAME = 'multi_test'
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    },
    'db1': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': DBNAME,
        'USER': 'root',
        'PASSWORD': 'xxx',
        'HOST': '127.0.0.1',
        'PORT': 3306,
        'OPTIONS': {
            'init_command': "SET sql_mode='STRICT_TRANS_TABLES'",
        },
    },
    'db2': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': DBNAME,
        'USER': 'root',
        'PASSWORD': 'xxx',
        'HOST': '127.0.0.1',
        'PORT': 5432,
    },
    'db3': {
        'ENGINE': 'django.db.backends.dummy',
    },
}
connect(DBNAME) #connect to mongodb
SUB_DIR = os.path.basename(os.path.dirname(__file__))
DATABASE_ROUTERS = [
    '{}.database_router.DatabaseAppsRouter'.format(SUB_DIR)
]
DATABASE_APPS_MAPPING = {
        # example:
        #'app_label':'database_name',
        'mysql': 'db1',
        'postgres': 'db2',
}
# 'mysql', 'postgres'需加到INSTALLED_APPS中，它們是通過startapp創(chuàng)建的兩個空app

在settings同目錄下增加database_router.py 文件，內(nèi)容如下：
（直接從自強學堂拷貝，只注釋掉print語句，無需做其他更改）

# -*- coding: utf-8 -*-
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.
        根據(jù)app_label的值只在相應(yīng)的數(shù)據(jù)庫中創(chuàng)建一個表，如果刪除該def或
        不指定過濾條件，則一個Model會在每個數(shù)據(jù)庫里都創(chuàng)建一個表。
        """
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(app_label) == db
        elif app_label in DATABASE_MAPPING:
            return False
        return None

models里在class Meta中指定app_label就可以指定它要使用的數(shù)據(jù)庫

例如：settings的DATABASE_APPS_MAPPING中指定app1對應(yīng)db1、app2對應(yīng)db2，
那么app1中的Model默認使用db1，而當指定Meta中的app_label為app2時，則改用db2。
注：app_label指定的值須包含在settings的INSTALLED_APPS中，否則makemigrations不會自動創(chuàng)建表。
app1/models.py內(nèi)容如下：

#coding=utf-8
from django.db import models
from django.utils.encoding import python_2_unicode_compatible

@python_2_unicode_compatible
class Animal(models.Model):
    name = models.CharField(max_length=20)

    def __str__(self):
        return self.name

    class Meta:
        # 通過app_label來指定要使用的數(shù)據(jù)庫
        # 需指定db_table，否則該class的表名會是mysql_animal
        # 如果不指定Meta的app_label，會使用默認數(shù)據(jù)庫
        app_label = 'mysql' 
        db_table = 'app1_animal'

@python_2_unicode_compatible
class Plant(models.Model):
    name = models.CharField(max_length=20)

    def __str__(self):
        return self.name

    class Meta:
        app_label = 'postgres'
        db_table = 'app1_plant'

app2/models.py

#coding=utf-8
from django.db import models
from django.utils.encoding import python_2_unicode_compatible

@python_2_unicode_compatible
class Fruit(models.Model):
    name = models.CharField(max_length=20)

    def __str__(self):
        return self.name

    class Meta:
        app_label = 'mysql'  #使用mysql數(shù)據(jù)庫
        db_table = 'app2_fruit'  #指定表名為app2_fruit

@python_2_unicode_compatible
class Nut(models.Model):
    name = models.CharField(max_length=20)

    def __str__(self):
        return self.name

    class Meta:
        app_label = 'postgres'  #使用postgres數(shù)據(jù)庫
        db_table = 'app2_nut'  #指定表名為app2_fruit

app1/test.py

from django.test import TestCase

from app1.models import Animal, Plant
from app2.models import Fruit, Nut

class ModelsTestCase(TestCase):
    # db1 -- mysql
    # db2 -- postgres
    def setUp(self):
        Animal.objects.create(name='db1')
        Plant.objects.create(name='db2')
        Fruit.objects.create(name='mysql_fruit')
        Nut.objects.create(name='post_nut')

    def test_methods_auto_choose_db(self):
        self.assertEqual(Animal.objects.all()[0],
                Animal.objects.using('db1').all()[0])
        self.assertEqual(Plant.objects.all()[0],
                Plant.objects.using('db2').all()[0])
        self.assertEqual(Fruit.objects.all()[0],
                Fruit.objects.using('db1').all()[0])
        self.assertEqual(Nut.objects.all()[0],
                Nut.objects.using('db2').all()[0])

        self.assertNotEqual(Animal.objects.all()[0],
                Fruit.objects.using('db1').all()[0])
        self.assertNotEqual(Plant.objects.all()[0],
                Nut.objects.using('db2').all()[0])
        self.assertNotEqual(Fruit.objects.all()[0],
                Plant.objects.using('db2').all()[0])

然后在命令行中運行

python manage.py makemigrations
python manage.py migrate --database=db1
python manage.py migrate --database=db2
python manage.py migrate
python manage.py test

完整代碼放在coding上：

git clone https://git.coding.net/zhengwenjie/multi_dbs.git
cd multi_dbs
virtualenv venv
source venv/bin/activate
pip install -r requirements.txt
vi multi_dbs/settings.py #修改數(shù)據(jù)庫名和密碼等
alias mg='python manage.py'
mg makemigrations
mg migrate --database=db1
mg migrate --database=db2
mg migrate
mg test

方式二：通過using手動指定數(shù)據(jù)庫

例如settings中的數(shù)據(jù)庫配置如下：

# Database
# https://docs.djangoproject.com/en/1.11/ref/settings/#databases

import pymysql
pymysql.install_as_MySQLdb()
from mongoengine import connect
DBNAME = 'multi_test'
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    },
    'mysql': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': DBNAME,
        'USER': 'root',
        'PASSWORD': 'xxx',
        'HOST': '127.0.0.1',
        'PORT': 3306,
        'OPTIONS': {
            'init_command': "SET sql_mode='STRICT_TRANS_TABLES'",
        },
    },
    'postgres': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': DBNAME,
        'USER': 'root',
        'PASSWORD': 'xxx',
        'HOST': '127.0.0.1',
        'PORT': 5432,
    },
    'mongo': {
        'ENGINE': 'django.db.backends.dummy',
    },
}

則查詢和創(chuàng)建數(shù)據(jù)語句如下（不加using為采用default數(shù)據(jù)庫）

from app1.models import House
House.objects.using('mysql').create(name='Tom')
House.objects.using('mysql').get(name='Tom')
House.objects.using('postgres').get_or_create(name='Jim')
最后編輯于 ：
?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者
【社區(qū)內(nèi)容提示】社區(qū)部分內(nèi)容疑似由AI輔助生成，瀏覽時請結(jié)合常識與多方信息審慎甄別。
平臺聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點，簡書系信息發(fā)布平臺，僅提供信息存儲服務(wù)。

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容