我有一个现有的DB,它有两个表,名为Identities和Accounts,我正试图使用Django ORM来管理它们。
Identities与Accounts有一对多的关系,我对这两个表进行了如下建模:
class Identity(models.Model):
class Meta:
managed = False
db_table = "Identities"
i_id = models.AutoField(db_column = "I_ID", primary_key = True)
name = models.CharField(db_column = "DisplayName", max_length = 200)
class Account(models.Model):
class Meta:
managed = False
db_table = "Accounts"
name = models.CharField(db_column = "Name", max_length = 200, primary_key = True)
identity = models.ForeignKey("Identity", db_column = "I_ID", blank = True, null = True, related_name = "accounts")
我的问题是,当我更新与帐户关联的身份时,所有与新身份关联的帐户都将切换到新身份:
old_identity = Identity.objects.create(name = "Old")
new_identity = Identity.objects.create(name = "New")
account_1 = Account.objects.create(name = "account_1", identity = old_identity)
account_2 = Account.objects.create(name = "account_2", identity = old_identity)
# change the identity for account_1:
account_1.identity = new_identity
account_1.save()
# read account_2 from DB and check identity
account_2 = Account.objects.get(name = "account_2")
# identity is now "New" also for account_2!
print account_2.identity.name
如果我直接在DB中进行相同的更新,那么只有我更改的帐户的身份发生了更改,而不是所有与该身份相关的帐户,所以这是Django引入的。
更改identity
字段时,如果只更新一个帐户,该怎么办?
注意:需要明确的是,数据库中的两个引用也都发生了更改,这不是数据未刷新之类的问题。
从已发布的相关代码中检查问题。发布的代码按预期运行:
创建表格:
(venv)dani@egg-v3:~/tmp/lldldl/paolo$ python manage.py migrate
Operations to perform:
Synchronize unmigrated apps: mytest
Apply all migrations: admin, contenttypes, auth, sessions
Synchronizing apps without migrations:
Creating tables...
Creating table mytest_identity
Creating table mytest_account
Installing custom SQL...
Installing indexes...
Running migrations:
Applying contenttypes.0001_initial... OK
Applying auth.0001_initial... OK
Applying admin.0001_initial... OK
Applying sessions.0001_initial... OK
运行:
(venv)dani@egg-v3:~/tmp/lldldl/paolo$ python manage.py shell
Python 2.7.3 (default, Feb 27 2014, 19:58:35)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from mytest.models import Account,Identity
>>> old_identity = Identity.objects.create(name = "Old")
>>> new_identity = Identity.objects.create(name = "New")
>>> account_1 = Account.objects.create(name = "account_1",
identity = old_identity)
>>> account_2 = Account.objects.create(name = "account_2",
identity = old_identity)
>>>
>>> # change the identity for account_1:
>>> account_1.identity = new_identity
>>> account_1.save()
>>>
>>> # read account_2 from DB and check identity
>>> account_2 = Account.objects.get(name = "account_2")
>>>
>>> # identity is now "New" also for account_2!
>>> print account_2.identity.name
Old
>>>
使用django 1.7和sqlite3进行了测试。也许是一些数据库触发器?后置/预存信号?