Django 1.9 在迁移中删除外键

问题描述

我有一个 Django 模型，它具有另一个模型的外键:

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

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

我想将底层的DB列保留为字段，但要摆脱数据库中的外键约束.

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

所以模型会变成:

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

而且，需要明确的是，something_id 是 Django 为外键字段创建的列.

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

我不想删除该列并重新创建它(这是 Django 在如上所述更改模型后自动生成迁移时所做的).

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).

我想保留字段但是我想通过迁移移除数据库中的外键约束.我不清楚如何使用 Django 迁移来做到这一点 - 是否有一些内置支持，或者我是否必须运行一些原始 SQL，如果是，我如何以编程方式获取约束的名称?

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?

推荐答案

这是我设法做到的，它基于上面nimasmi的回答:

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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