How to make email field unique in model User from contrib.auth in Django

Question

I need to patch the standard User model of contrib.auth by ensuring the email field entry is unique:

User._meta.fields[4].unique = True
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Answer 1

To ensure a User, no matter where, be saved with a unique email, add this to your models:

@receiver(pre_save, sender=User)
def User_pre_save(sender, **kwargs):
    email = kwargs['instance'].email
    username = kwargs['instance'].username

    if not email: raise ValidationError("email required")
    if sender.objects.filter(email=email).exclude(username=username).count(): raise ValidationError("email needs to be unique")

Note that this ensures non-blank email too. However, this doesn't do forms validation as would be appropriated, just raises an exception.

Answer 2

One possible way to do this is to have a pre-save hook on the User object and reject the save of the email already exists in the table.

Answer 3

In settings module:

# Fix: username length is too small,email must be unique
from django.contrib.auth.models import User, models
User._meta.local_fields[1].__dict__['max_length'] = 75
User._meta.local_fields[4].__dict__['_unique'] = True

Answer 4

Add somewhere this:

User._meta.get_field_by_name('email')[0]._unique = True     

and then execute SQL similar to this:

ALTER TABLE auth_user ADD UNIQUE (email);

Answer 5

What about using unique_together in a "different" way? So far it works for me.

class User(AbstractUser):
    ...
    class Meta(object):
        unique_together = ('email',)

Answer 6

Simply use below code in models.py of any app

from django.contrib.auth.models import User
User._meta.get_field('email')._unique = True