Altering Models with Migrations

Adding a New Field

Adding a field to a model and running makemigrations generates an AddField operation. If existing rows exist and the field isn't nullable, Django will prompt for a one-time default value during makemigrations.

Example: Adding a New Field

Giving subtitle a default='' means existing Article rows get an empty subtitle automatically instead of makemigrations asking for one interactively.

class Article(models.Model):
    title = models.CharField(max_length=200)
    subtitle = models.CharField(max_length=200, default='')

Removing a Field

Deleting a field from the model and running makemigrations generates a RemoveField operation, which drops that column — and all its data — from the table when migrate runs.

Warning: Once a RemoveField migration is applied, that column's data cannot be recovered.

Example: Removing a Field

After removing a field from Article in models.py, this pair of commands generates and then applies the RemoveField migration.

python manage.py makemigrations blog
python manage.py migrate blog

Renaming a Field

When makemigrations detects a field was removed and a similarly-typed one was added in the same run, it asks whether this is actually a rename, which preserves existing data instead of losing it.

Note: Answer y to the rename prompt to keep existing data; answering n creates a new empty column instead.

Example: Renaming a Field

Confirming the rename produces a RenameField operation, which keeps every existing row's data instead of dropping and recreating the column.

python manage.py makemigrations
# Did you rename article.title to article.headline? [y/N]