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Django 1.9 removes foreign key during migration

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

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

I want to save the base column of the database 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_idthis is the column created by Django for the foreign key field.

I don’t want to drop the column and recreate it (this is what Django does when I automatically generate the migration after changing the model as above).

I want to keep the field, but I want to remove the foreign key constraint in the wrap database. I don’t understand how to do this with Django porting - is there any built-in support for it or do I need to run some raw SQL, and if so, how can I programmatically get the name of the constraint?

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2 answers

Here's how I did it, it is 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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See SeparateDatabaseAndState . It allows you to specify part of the Django (state) migration separately from the database part of the migration.

  • Change the field in the model file.

  • Create the migration as usual. You will get something like:

    class Migration(migrations.Migration):

    dependencies = [
        ('my_app', '0001_whatever.py'),
    ]

    operations = [
        migrations.AlterField(
            model_name='example',
            name='something',
            field=models.CharField(max_length=255, null=True)),
        ),
    ]

  • :

    class Migration(migrations.Migration):

    dependencies = [
        ('my_app', '0001_whatever.py'),
    ]

    state_operations = [
        migrations.AlterField(
            model_name='example',
            name='something',
            field=models.CharField(max_length=255, null=True)),
        ),
    ]
    operations = [
        migrations.SeparateDatabaseAndState(state_operations=state_operations)
    ]

, - database_operations, Django , .

: , .

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