django db_index for foreign key reverse lookup

Let's say the you have a simple model structure:

class Author(models.Model):
   name = models.CharField(max_length = 70)
email = models.EmailField()

class Book(models.Model):
   title = models.CharField(max_length = 100)
author = models.ForeignKey(Author)

Now querying:

author_books = Book.objects.filter(author = a)

author_books = a.book_set.all()

Suggestion : 2

For fields like ForeignKey that map to model instances, defaults should be the value of the field they reference (pk unless to_field is set) instead of model instances.,Set this to the name of a DateField or DateTimeField to require that this field be unique for the value of the date field.,The default value is used when new model instances are created and a value isn’t provided for the field. When the field is a primary key, the default is also used when the field is set to None.,It should return the value of the appropriate attribute from model_instance for this field. The attribute name is in self.attname (this is set up by Field).

YEAR_IN_SCHOOL_CHOICES = [
   ('FR', 'Freshman'),
   ('SO', 'Sophomore'),
   ('JR', 'Junior'),
   ('SR', 'Senior'),
   ('GR', 'Graduate'),
]

from django.db
import models

class Student(models.Model):
   FRESHMAN = 'FR'
SOPHOMORE = 'SO'
JUNIOR = 'JR'
SENIOR = 'SR'
GRADUATE = 'GR'
YEAR_IN_SCHOOL_CHOICES = [
   (FRESHMAN, 'Freshman'),
   (SOPHOMORE, 'Sophomore'),
   (JUNIOR, 'Junior'),
   (SENIOR, 'Senior'),
   (GRADUATE, 'Graduate'),
]
year_in_school = models.CharField(
   max_length = 2,
   choices = YEAR_IN_SCHOOL_CHOICES,
   default = FRESHMAN,
)

def is_upperclass(self):
   return self.year_in_school in {
      self.JUNIOR,
      self.SENIOR
   }

MEDIA_CHOICES = [
   ('Audio', (
      ('vinyl', 'Vinyl'),
      ('cd', 'CD'),
   )),
   ('Video', (
      ('vhs', 'VHS Tape'),
      ('dvd', 'DVD'),
   )),
   ('unknown', 'Unknown'),
]

from django.utils.translation
import gettext_lazy as _

class Student(models.Model):

   class YearInSchool(models.TextChoices):
   FRESHMAN = 'FR', _('Freshman')
SOPHOMORE = 'SO', _('Sophomore')
JUNIOR = 'JR', _('Junior')
SENIOR = 'SR', _('Senior')
GRADUATE = 'GR', _('Graduate')

year_in_school = models.CharField(
   max_length = 2,
   choices = YearInSchool.choices,
   default = YearInSchool.FRESHMAN,
)

def is_upperclass(self):
   return self.year_in_school in {
      self.YearInSchool.JUNIOR,
      self.YearInSchool.SENIOR,
   }

>>> class Vehicle(models.TextChoices):
   ...CAR = 'C'
   ...TRUCK = 'T'
   ...JET_SKI = 'J'
   ...
   >>>
   Vehicle.JET_SKI.label 'Jet Ski'

class Card(models.Model):

   class Suit(models.IntegerChoices):
   DIAMOND = 1
SPADE = 2
HEART = 3
CLUB = 4

suit = models.IntegerField(choices = Suit.choices)

Suggestion : 3

Currently reverse ForeignKey lookups are impossible for models which are related to other models more than once. Could this be fixed by using the related_name instead of the model's name for resolving the one-to-many lookup? , On a related note: It seems inconsistent to me that two ForeignKeys related to the same model result in a reverse lookup exception but, e.g., a ForeignKey and a ManyToMany-Field related to the same model don't raise the "TypeError: Can't resolve keyword" exception (the ManyToManyField is used, the ForeignKey ignored). , This seems to work in the current version of magic-removal, great! I have attached the unit tests that demonstrate that it works (and make sure it doesn't break). , (In [2280]) magic-removal: Fixed #1305 -- Added new unit test group for reverse lookup queries over foreign keys. Thanks, Andreas.

class Poll(models.Model):
   question = models.CharField(maxlength = 200)

class Choice(models.Model):
   name = models.CharField(maxlength = 100)
poll = models.ForeignKey(Poll, related_name = "choice")
related_poll = models.ForeignKey(Poll, related_name = "related_choice")

class Poll(models.Model):
    question = models.CharField(maxlength=200)

class Choice(models.Model):
    name = models.CharField(maxlength=100)
    poll = models.ForeignKey(Poll, related_name="choice")
    related_poll = models.ForeignKey(Poll, related_name="related_choice")

first_poll = Poll(question = "What's the first question?")
first_poll.save()
second_poll = Poll(question = "What's the second question?")
second_poll.save()
new_choice = Choice(
   poll = first_poll,
   related_poll = second_poll,
   name = "This is the answer."
)
new_choice.save()

# The current state:
   try:
   Poll.objects.get_object(choice__name__exact = "This is the answer.")
except TypeError:
   # raises TypeError with "Cannot resolve keyword 'choice' into field"
# because more than one field could be identified by "choice"
pass

# How it could be(lookups by related_name):
   Poll.objects.get_object(choice__name__exact = "This is the answer.") # returns first poll
Poll.objects.get_object(related_choice__name__exact = "This is the answer.") # returns second poll