Question

Previously I had a django model like this

class Review(models.Model):
    reviewdate=models.DateField(default=date.today)
    description=models.TextField()
    author=models.ForeignKey(User,null=True)

I have some 500 records of Review in db.

I added a field to model

from django.core.validators import MinValueValidator,MaxValueValidator

class Review(models.Model):
    reviewdate=models.DateField(default=date.today)
    description=models.TextField()
    author=models.ForeignKey(User,null=True)
    rating= models.IntegerField(validators=[MinValueValidator(1), MaxValueValidator(10)], default=5, help_text='integers 1 to 10')

I ran python manage.py schemamigration myapp --auto successfully ,which created a 0002_auto__add_field_review_rating.py file

Now, I need to do the datamigration for the existing records in db. Do I have to run

python manage.py datamigration myapp somechanges

and then implement the functions in the created somechanges.py ? Since I have already defined in the new field difficulty a default value of 5, will that not be taken when migrate command is run? Do I have to explicitly set it in the somechanges.py functions?

Answer 1

You do not need to do a data migration for this case. As you have specified a default for your new field, that will be used when you apply the schema migration.

Use the following command to apply the migration:

./manage.py migrate myapp

See the advanced changes South tutorial for more information on default values for new fields.