Cannot add foreign key constraint when migrating manytomany field

[Ville Säävuori]

I have a model that looks like

class LiveEvent(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    ...
    attendees = models.ManyToManyField(
        User, blank=True, related_name="events_attended"
    )
    ...
    notify_subscriptions = models.ManyToManyField(
        User, blank=True, related_name="events_subscribed"
    )

when trying to add and migrate notify_subscriptions field I get the following error:

django.db.utils.IntegrityError: (1215, 'Cannot add foreign key constraint')`

When adding

'OPTIONS': {
    "init_command": "SET foreign_key_checks = 0;",
},

to database settings , the error became:

django.db.utils.OperationalError: (1825, "Failed to add the foreign key constraint on table 'levan_liveevent_notify_subscriptions'. Incorrect options in FOREIGN KEY constraint 'slipmat/levan_liveevent_noti_liveevent_id_a4871abc_fk_levan_liveevent_id'")

the migration file looks like:

operations = [
    migrations.AddField(
        model_name='liveevent',
        name='notify_subscriptions',
        field=models.ManyToManyField(
            blank=True, related_name='events_subscribed', to=settings.AUTH_USER_MODEL
        ),
    ),
]

I'm using MySQL version 5.6.27 and Django version 1.9.7

[Simon Charette]

I just tried reproducing against Django 1.9.7 with no success.

Please re-open the ticket by answering these two questions:

1. Are both of your tables using the InnoDB engine? Foreign keys are not supported on MyISAM.
2. Are you using a custom user model which you didn't provide the definition?

[Ville Säävuori]

1. Yes, both tables are using InnoDB engine.
2. No, I'm not using a custom user model

[Ville Säävuori]

FWIW, adding db_constraint=False to the notify_subscriptions field produces a migration that runs flawlessly. That's my workaround for now.

[Simon Charette]

Are you using Oracle's MySQL backend or django.db.backends.mysql?

[Simon Charette]

Please inspect your database and provide us with the datatype of both LiveEvent's table id column and the intermediary table's (notify_subscriptions) column referencing the former.