【Python教程】Django项目如何配置连接多个数据库方法

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Python

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教程如下

一个APP对应一个默认数据库,若连接其他数据库用”.using()”


 	Author.objects.using('db02').all()

1、在项目settings中增加数据库配置


 	# settings.py
 	
 	DATABASES = {
 	     'default': {
 	     'ENGINE': 'django.db.backends.oracle',
 	         'NAME': 'orcl19c',
 	         'USER': "username01",
 	         'PASSWORD': "password01",
 	         'HOST': "110.10.1.11",
 	         'PORT': 1511,
 	     },
 	     'db_2': {
 	     'ENGINE': 'django.db.backends.oracle',
 	         'NAME': 'orcl19c',
 	         'USER': "username02",
 	         'PASSWORD': "password02",
 	         'HOST': "120.20.2.22",
 	         'PORT': 1512,
 	     }
 	}
 	# 以下MyProject改成项目名,默认default不用修改
 	DATABASE_ROUTERS = ['MyProject.database_router.DatabaseAppsRouter']
 	DATABASE_APPS_MAPPING = {
 	     'app01': 'default',
 	     'app02': 'db_2',
 	}

2、在项目根目录下Myproject/Myproject 新建数据库路由文件database_router.py

直接复制以下代码,无需修改


 	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
 	
 	     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

3、使用inspectdb反向生成各app的model类之后,配置model类对应要链接的数据库

反向生成models.py 命令:


 	python manage.py inspectdb --database db1 TableName1 > app01/models.py
 	
 	python manage.py inspectdb --database db2 TableName2 > app02/models.py

 


 	# 编辑app01下的models.py:
 	class Names(models.Model): #该model使用default数据库
 	     id=models.CharField(primary_key=True,max_length=100, blank=True, null=True)
 	     name=models.CharField(max_length=32,primary_key=True,unique=True)
 	
 	     class Meta:
 	         #app_label = 'app01' #由于该model连接default数据库,所以在此无需指定
 	         db_table = 'names'
 	
 	# 编辑app02下的models.py:
 	class Classnum(models.Model): #该model使用default数据库
 	     id=models.CharField(primary_key=True,max_length=100, blank=True, null=True)
 	     classnum=models.CharField(max_length=32,primary_key=True,unique=True)
 	
 	     class Meta:
 	         app_label = 'app02'
 	         db_table = 'classnum'

4、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

5、若要连接配置外的数据库


 	Author.objects.using('other').all()
 	my_object.save(using='legacy_users')
 	my_object.delete(using='legacy_users')

移动对象到另一个数据库时会发生主键冲突,可以使用obj.pk方法清除主键再保存对象


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

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