Querying across Generic Relations

[Lee Hinde]

I have a table, Credit, that I want to query based on a value several hops away. There's a CreditLineItems that has a Generic Foreign Key to one of two tables, each of which has a Foreign Key to the table I want to search. I've not as yet setup a reverse relation in the related tables.

My question is, given the structure below, how do I return a selection of Credits based on a value in Registration?

class Credit(models.Model):

""" Model queried """

    

class CreditLineItem(models.Model):

    credit = models.ForeignKey(Credit)

    content_type = models.ForeignKey(ContentType)

    object_id = models.PositiveIntegerField()

    content_object = generic.GenericForeignKey('content_type', 'object_id')  #assumed values...

# The GenericForeignKey could point to

class Enrollment(models.Model):

    registration = models.ForeignKey(Registration, blank=True)

--OR--

class ProductSale(models.Model):

    registration = models.ForeignKey(Registration, blank=True)

class Registration(models.Model):

    registration_number =  models.IntegerField(db_index=True)