Odd behaviour with ForeignKey to non-integer field since Django 2.0.5 with PostgreSQL

[Henrik Ossipoff Hansen]

I was upgrading one of our projects from 1.11.x to the newest Django 2.0.x when encountering a rather odd thing - all of our tests were literally failing with seemingly a database error:

django.db.utils.DataError: value "1111222233334444" is out of range for type integer

The field, however, is not an integer field, but rather a char field - so that particular string shouldn't be of any problem - and the fact that it appears to report back being an integer field is rather bizarre.

While I know that this error returned is simply a psycopg2.DataError in disguise, it turns out that this error seem to have been introduced in 2.0.5 specifically - all of our tests passes in 2.0.4.

The slight problem here is that I've been unable to reproduce a minimal working example that can reproduce the error, even though it's really consistent for us.

Our models look something like this (simplified):

class Giftcard(Model):
    STATUS_CREATED = 'CREATED'
    STATUS_ACTIVATED = 'ACTIVATED'
    STATUS_SUSPENDED = 'SUSPENDED'
    STATUS_EXPIRED = 'EXPIRED'
    STATUS_CLOSED = 'CLOSED'

    STATUS_CHOICE = (
        (STATUS_CREATED, 'Created'),
        (STATUS_ACTIVATED, 'Activated'),
        (STATUS_SUSPENDED, 'Suspended'),
        (STATUS_EXPIRED, 'Expired'),
        (STATUS_CLOSED, 'Closed'),
    )

    code = models.CharField(max_length=16, primary_key=True)
    status = models.CharField(max_length=20, choices=STATUS_CHOICE, default=STATUS_CREATED, db_index=True)

    def status_change(self, reason, to):
        StatusChangeLog.objects.create(giftcard=self, reason=reason, from_status=self.status, to_status=to)

class StatusChangeLog(Model):
    giftcard = models.ForeignKey('giftcards.Giftcard', related_name='status_logs', on_delete=models.PROTECT)
    reason = models.TextField(blank=True, default='')
    from_status = models.CharField(max_length=20, choices=Giftcard.STATUS_CHOICE)
    to_status = models.CharField(max_length=20, choices=Giftcard.STATUS_CHOICE)

When the Giftcard model is instantiated with a code of "1111222233334444" (as a string), saved, and then the status_change method is called, the above exception occurs.

I've been through some of code that went into 2.0.5, but I'm not well enough into the inner workings of Django know exactly what caused this - I just know that this behaviour wasn't in 1.11.x, and also wasn't in 2.0.4.

[Alexandr Tatarinov]

Cannot reproduce at 2.0.5 with PostgreSQL.Try to bisect to find the commit at which tests starts to fail.

[Henrik Ossipoff Hansen]

I've bisected the commit to be ​d5018abf1c4e3c68f1a825d05eb9035325707e16

I'm not entirely sure why this commit in particular is causing problems though - and I'm a bit puzzled that we're unable to reproduce it with a "clean" model. Could this mean it's related to applying the migration history during our unit tests?

I suppose I could try to get together a working test set tomorrow.

[Tim Graham]

Yes, it looks like it's related to migrations and an AlterField operation.

[Tim Graham]

Please reopen when you provide a sample project and confirm that Django is at fault.