Django - 如何防止创建数据库外键约束 [英] Django - How to prevent database foreign key constraint creation

问题描述

我有一个由数据库视图支持的模型。

I have a model that is backed by a database view.

class OrgCode(models.Model):
    org_code                = models.CharField(db_column=u'code',max_length=15) 
    org_description         = models.CharField(max_length=250)
    org_level_num           = models.IntegerField()

    class Meta:
        db_table = u'view_FSS_ORG_PROFILE'

我需要在另一个模型

class AssessmentLocation(models.Model):
    name                = models.CharField(max_length=150)
    org                 = models.ForeignKey(OrgCode)

我无法运行syncdb，因为外键限制不能创建引用视图。

I can't run syncdb because foreign key constraints cannot be created referencing a view.

 u"Foreign key 'FK__main_asse__org__1D114BD1' 
 references object 'view_FSS_ORG_PROFILE' 
 which is not a user table.", None, 0, -214
7217900), None)
Command:
CREATE TABLE [main_assessmentlocation] (
    [id] int IDENTITY (1, 1) NOT NULL PRIMARY KEY,
    [name] nvarchar(150) NOT NULL,
    [org] int NOT NULL REFERENCES [view_FSS_ORG_PROFILE] ([id]),
)

解决方法是取出Meta：db_table指向视图，并让db同步创建OrgCode表，然后将Meta：db_table重新置于syncdb之后。

The workaround is to take out the Meta:db_table pointing to the view and let sync db create the the OrgCode table, then put the Meta:db_table back in after syncdb.

有没有办法阻止某些型号或字段创建外键限制？

Is there a way to prevent the creation of foreign key constraints for certain models or fields?

更新：我向相关模型添加了一个静态方法，表示它是一个视图

Update: I added a static method to the related model indicating it's a view

class OrgCode(models.Model):
    org_code                = models.CharField(max_length=15)
    org_description         = models.CharField(max_length=250)

    @staticmethod
    def is_backend_view():
        return True

然后在django_mssql中覆盖DatabaseCreation.sql_for_inline_foreign_key_references creation.py：

Then overrode DatabaseCreation.sql_for_inline_foreign_key_references in django_mssql creation.py:

def sql_for_inline_foreign_key_references(self, field, known_models, style):
    try: 
        field.rel.to.is_backend_view()
        return "", False
    except:
        return super(DatabaseCreation,self).sql_for_inline_foreign_key_references(field, known_models, style)    

来自syncdb的生成的sql会留下限制：

The generated sql from syncdb leaves out the constraint:

CREATE TABLE [main_assessmentlocation] (
    [id] int IDENTITY (1, 1) NOT NULL PRIMARY KEY,
    [name] nvarchar(150) NOT NULL,
    [org] int, -- NO FK CONSTRAINT ANYMORE --
);

它涉及黑客django_mssql，所以我要继续尝试，也许挂在django。 db.backends.signals.connection_created信号将工作...

It does involve hacking django_mssql so I'm going to keep on trying, maybe hooking into the django.db.backends.signals.connection_created signal will work...

推荐答案

django开发版本有一个 db_constraint 字段 ForeignKey 模型字段 - docs 。

django development version has a db_constraint field for ForeignKey model field - docs.

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