Django migration converting integer pk table to UUID pk table

django_migration_pk_to_uuid.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals
import uuid

from django.db import migrations, models


def fill_mymodel_uuid(apps, schema_editor):
    db_alias = schema_editor.connection.alias
    MyModel = apps.get_model('myapp', 'MyModel')
    for obj in MyModel.objects.using(db_alias).all():
        obj.uuid = uuid.uuid4()
        obj.save()


class Migration(migrations.Migration):
    """ Change model with integer pk to UUID pk.  This migration presumes there
    are no db constraints (foreign keys) to this table.
    
    Note: this migration is not reversible.  See the comment above the
    `RemoveField` operation.  Further, this migration is possible in part due
    to the fact that there are currenty no foreign key restraints to this table.
    """

    dependencies = [
        # ...
    ]

    operations = [
        migrations.AddField(
            model_name='mymodel',
            name='uuid',
            field=models.UUIDField(null=True),
        ),
        migrations.RunPython(fill_mymodel_uuid, migrations.RunPython.noop),
        migrations.AlterField(
            model_name='mymodel',
            name='uuid',
            field=models.UUIDField(default=uuid.uuid4, serialize=False, editable=False, unique=True),
        ),
        # this RemoveField operation is irreversible, because in order to
        # recreate it, the primary key constraint on the UUIDField would first
        # have to be dropped.
        migrations.RemoveField('MyModel', 'id'),
        migrations.RenameField(
            model_name='mymodel',
            old_name='uuid',
            new_name='id'
        ),
        migrations.AlterField(
            model_name='mymodel',
            name='id',
            field=models.UUIDField(primary_key=True, default=uuid.uuid4, serialize=False, editable=False, unique=True),
        ),
    ]

Removing the unique=True in lines 39 and 53 made the migration reversible for me. For some reason, this allows the primary key constraint on the UUIDField to be dropped.

Removing the unique=True in lines 39 and 53 made the migration reversible for me. For some reason, this allows the primary key constraint on the UUIDField to be dropped.

how do you deal with foreign keys?

how do you deal with foreign keys?

Thank you bro!

Thank you bro!

@PFischbeck: a primary key has to be unique. Don't know how you plan to use it as a primary key without uniqueness constraint.

@PFischbeck: a primary key has to be unique. Don't know how you plan to use it as a primary key without uniqueness constraint.