BigAutoField – Django Models

BigAutoField is a 64-bit integer, much like an AutoField except that it is guaranteed to fit numbers from 1 to 9223372036854775807. One can create a BigAutoField using the following syntax,

id = models.BigAutoField(primary_key=True, **options)

This is an auto-incrementing primary key just like AutoField.

Django Model BigAutoField Explanation

Illustration of BigAutoField using an Example. Consider a project named geeksforgeeks having an app named geeks.



Refer to the following articles to check how to create a project and an app in Django.

Enter the following code into models.py file of geeks app.

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from django.db import models
from django.db.models import Model
# Create your models here.
  
class GeeksModel(Model):
    big_id = models.BigAutoField(primary_key = True)

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Add the geeks app to INSTALLED_APPS

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# Application definition
  
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'geeks',
]

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Now when we run makemigrations command from the terminal,

Python manage.py makemigrations

A new folder named migrations would be created in geeks directory with a file named 0001_initial.py

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# Generated by Django 2.2.5 on 2019-09-25 06:00
  
from django.db import migrations, models
  
class Migration(migrations.Migration):
  
    initial = True
  
    dependencies = [
    ]
  
    operations = [
        migrations.CreateModel(
            name ='GeeksModel',
            fields =[
                ('big_id'
                  models.BigAutoField(auto_created = True,
                  primary_key = True,
                  serialize = False
                  verbose_name ='ID'
                )),
            ],
        ),
    ]

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Thus, an big_id BigAutoField that auto increments on every instance of that model is created when you run makemigrations on the project. It is a primary key to the table created for the model named GeeksModel.

Possible Error
since a Django model can have at most one autofield, BigAutoField must be created at the very first migration with primary_key=True attribute otherwise it will raise multiple errors.

“AssertionError: A model can’t have more than one AutoField.”

If you get this error try deleting the recent migrations and adding primary_key=True to the field. Run Migrations again to solve the problem.

If we create objects of this empty model from the admin server. we can see id field autoincrementing on every instance created.
Django-model-autofield

Field Options

Field Options are the arguments given to each field for applying some constraint or imparting a particular characteristic to a particular Field. For example, adding an argument primary_key=True to BigAutoField will make it primary key for that table in relational database.
Here are the option and attributes that an BigAutofield can use.

Field Options Description
Null If True, Django will store empty values as NULL in the database. Default is False.
Blank If True, the field is allowed to be blank. Default is False.
Choices An iterable (e.g., a list or tuple) of 2-tuples to use as choices for this field.
Default The default value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created.
help_text Extra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form.
primary_key If True, this field is the primary key for the model.
Unique If True, this field must be unique throughout the table.


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