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BigAutoField – Django Models

  • Last Updated : 24 Aug, 2021

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. 



Python3




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)

Add the geeks app to INSTALLED_APPS 

Python3




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

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 

Python3




# 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'
                )),
            ],
        ),
    ]

Thus, a 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 the primary key for that table in a relational database. 
Here are the option and attributes that an BigAutofield can use.

Field OptionsDescription
NullIf True, Django will store empty values as NULL in the database. Default is False.
BlankIf True, the field is allowed to be blank. Default is False.
db_indexIf True, a database index will be created for this field.
db_tablespaceThe name of the database tablespace to use for this field’s index if this field is indexed. The default is the project’s DEFAULT_INDEX_TABLESPACE setting, if set, or the db_tablespace of the model if any. If the backend doesn’t support tablespaces for indexes, this option is ignored.
db_columnThe name of the database column to use for this field. If this isn’t given, Django will use the field’s name. 
 
DefaultThe 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_textExtra “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_keyIf True, this field is the primary key for the model.
editableIf False, the field will not be displayed in the admin or any other ModelForm. They are also skipped during model validation. Default is True
 
error_messagesThe error_messages argument lets you override the default messages that the field will raise. Pass in a dictionary with keys matching the error messages you want to override. 
 
help_textExtra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form. 
 
verbose_nameA human-readable name for the field. If the verbose name isn’t given, Django will automatically create it using the field’s attribute name, converting underscores to spaces. 
 
validatorsA list of validators to run for this field. See the validators documentation for more information. 
 
UniqueIf True, this field must be unique throughout the table. 
 

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