标签：get utils import 字典 hint inpu erb 个数 hit
很多时候,需要去其他数据库查询数据,都将会面临多数据库支持问题.
1.在settings文件内添加多数据库连接
DATABASES = { ‘default‘: { ‘ENGINE‘: ‘django.db.backends.sqlite3‘, ‘NAME‘: os.path.join(BASE_DIR, ‘db.sqlite3‘), }, ‘test‘: { ‘ENGINE‘: ‘django.db.backends.mysql‘, ‘NAME‘: ‘pro_control‘, ‘USER‘: ‘root‘, ‘PASSWORD‘: ‘root‘, ‘HOST‘: ‘10.0.11.11‘, ‘PORT‘: ‘3306‘, } }
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‘ } }
如果你试图连接一个没有在DATABASES内定义的数据库django将产生django.db.utils.ConnectionDoesNotExist异常
./manage.py migrate # 操作将同步到default数据库 ./manage.py migrate --database=test # 同步到test数据库
如果不是想所有的模型都同步到一个数据库上你可以定义一个database router,新建db_router.py文件
class AuthRouter: def db_for_read(self, model, **hits): if model._meta.app_label == ‘test01‘: return ‘test‘ return None def db_for_write(self, model, **hits): if model._meta.app_label == ‘test01‘: return ‘test‘ return None def allow_relation(self, obj1, obj2, **hits): if obj1._meta.app_label == ‘test01‘ or obj2._meta.app_label == ‘test01‘: return True return None def allow_migrate(self, db, app_label, model_name=None, **hits): if app_label == ‘test01‘: return db == ‘test‘ return None
在setting文件内添加DATABASE_ROUTERS参数
DATABASE_ROUTERS = [‘test01.db_router.AuthRouter‘, ]
为测试model指定,在test01的models文件内写入
from django.db import models import shortuuid # Create your models here. def createuuid(): return shortuuid.uuid() class CourseManage(models.Model): """课程管控表""" uuid = models.CharField( ‘ID‘, max_length=22, primary_key=True, default=createuuid, editable=False) add_time = models.DateTimeField(‘创建时间‘, auto_now_add=True) del_state_type = ((0, ‘已删除‘), (1, ‘默认‘)) modified_time = models.DateTimeField(‘修改时间‘, auto_now=True) del_state = models.IntegerField( ‘删除状态‘, choices=del_state_type, default=1, db_index=True) config_status = ((1, ‘进行中‘), (2, ‘完结‘), ) remote_id = models.CharField(verbose_name=‘远端产品id‘, max_length=30) status = models.PositiveSmallIntegerField(choices=config_status, default=1) class Meta: verbose_name = ‘课程‘ verbose_name_plural = verbose_name db_table = ‘backend_coursemanage‘
db_table指定此模型在远端的数据库内的表名称.不然会报错
按照上述操作,便能连接并查询.
标签:当项目需要执行python manage.py makemigrations时,会发现,test01项目的migrations文件夹会产生migrations文件.并且终端也会产生提示,
可以尝试删除此migrations,来避免这个问题,allow_migrate的判断只针对真正的migrate操作.
如何选择数据库?
User.objects.using(‘legacy_users‘).get(username=‘fred‘) user_obj.save(using=‘new_users‘) user_obj.delete(using=‘legacy_users‘)
2.原生光标
from django.db import connections with connections[‘my_db_alias‘].cursor() as cursor: ...
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‘, }, }
import random class PrimaryReplicaRouter: def db_for_read(self, model, **hints): """ Reads go to a randomly-chosen replica. """ return random.choice([‘replica1‘, ‘replica2‘]) # 这里是重点 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
标签：get utils import 字典 hint inpu erb 个数 hit
原文地址：https://www.cnblogs.com/wuzdandz/p/10791984.html
