Django 1.9在迁移时放弃了外键 [英] Django 1.9 drop foreign key in migration

问题描述

 类示例（models.Model）$ b我有一个Django模型，它有另一个模型的外键： $ b something = models.ForeignKey（SomeModel，db_index = True）
  

我想保留底层数据库列作为一个字段，但要摆脱数据库中的外键约束。

所以模型将改变为：

  class示例（models.Model）：
 something_id = models.IntegerField（）
  

显然， something_id 是Django为外键字段创建的列。 b
$ b

我不想删除列并重新创建它（这是Django在更改模型之后自动生成迁移时所做的工作）。

我想保留字段，但是我想通过迁移来删除数据库中的外键约束。我不清楚如何通过Django迁移来实现这一点 - 是否有一些内置的支持它，或者我必须运行一些原始的SQL，如果是这样，我怎样编程获取约束的名称？

解决方案

这是我设法做到的，它基于上面的nimasmi的答案：

  class Migration（migrations.Migration）：
 dependencies = [
（'my_app'，'0001_initial'），
] 
 
＃这些*将*影响数据库！ 
 database_operations = [
 migrations.AlterField（
 model_name ='Example'，
 name ='something'，
 field = models.ForeignKey（'Something'，db_constraint = False，db_index = True，null = False）
），
] 
 
＃这些*不会影响数据库，它们只会更新Django状态*！ 
 state_operations = [
 migrations.AlterField（
 model_name ='Example'，
 name ='something'，
 field = models.IntegerField（db_index = True，null = False）
），
 migrations.RenameField（
 model_name ='Example'，
 old_name ='something'，
 new_name ='something_id'
 ），
] 
 
 operations = [
 migrations.SeparateDatabaseAndState（
 database_operations = database_operations，
 state_operations = state_operations 
）
 ] 
  

I have a Django model that has a foreign key to another model:

class Example(models.Model)
   something = models.ForeignKey(SomeModel, db_index=True)

I want to keep the underlying DB column as a field, but to get rid of the foreign key constraint in the database.

So the model will change to:

class Example(models.Model):
   something_id = models.IntegerField() 

And, to be clear, something_id is the column that Django had created for the foreign key field.

I do not want to drop the column and re-create it (this is what Django does when I auto-generate migrations after changing the model as above).

I want to keep the field but I want to remove the foreign key constraint in the database with a migration. It's not clear to me how to do this with a Django migration - is there some built in support for it or do I have to run some raw SQL and, if so, how do I programatically get the name of the constraint?

解决方案

This is how I managed to do it, it's based on nimasmi's answer above:

class Migration(migrations.Migration):
    dependencies = [
        ('my_app', '0001_initial'),
    ]

    # These *WILL* impact the database!
    database_operations = [
        migrations.AlterField(
            model_name='Example',
            name='something',
            field=models.ForeignKey('Something', db_constraint=False, db_index=True, null=False)
        ),
    ]

    # These *WON'T* impact the database, they update Django state *ONLY*!
    state_operations = [
        migrations.AlterField(
            model_name='Example',
            name='something',
            field=models.IntegerField(db_index=True, null=False)
        ),
        migrations.RenameField(
            model_name='Example',
            old_name='something',
            new_name='something_id'
        ),
    ]

    operations = [
        migrations.SeparateDatabaseAndState(
            database_operations=database_operations,
            state_operations=state_operations
        )
    ]

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