I know that from Django 1.7 I don't need to use South or any other migration system, so I am just using simple command python manage.py makemigrations
However, all I get is this error:
You are trying to add a non-nullable field 'new_field' to userprofile without a default;
we can't do that (the database needs something to populate existing rows).
Here is models.py:
class UserProfile(models.Model):
user = models.OneToOneField(User)
website = models.URLField(blank=True)
new_field = models.CharField(max_length=140)
What are options?
In new_file add the boolean property null.
new_field = models.CharField(max_length=140, null=True)
after you run a ./manage.py syncdb for refresh the DB.
and finally you run ./manage.py makemigrations
and ./manage.py migrate
What Django actually says is:
Userprofile table has data in it and there might be
new_fieldvalues which are null, but I do not know, so are you sure you want to mark property as non nullable, because if you do you might get an error if there are values with NULL
If you are sure that none of values in the userprofile table are NULL - fell free and ignore the warning.
The best practice in such cases would be to create a RunPython migration to handle empty values as it states in option 2
2) Ignore for now, and let me handle existing rows with NULL myself (e.g. because you added a RunPython or RunSQL operation to handle NULL values in a previous data migration)
In RunPython migration you have to find all UserProfile instances with empty new_field value and put a correct value there (or a default value as Django asks you to set in the model).
You will get something like this:
# please keep in mind that new_value can be an empty string. You decide whether it is a correct value.
for profile in UserProfile.objects.filter(new_value__isnull=True).iterator():
profile.new_value = calculate_value(profile)
profile.save() # better to use batch save
Have fun!
Do you already have database entries in the table UserProfile? If so, when you add new columns the DB doesn't know what to set it to because it can't be NULL. Therefore it asks you what you want to set those fields in the column new_fields to. I had to delete all the rows from this table to solve the problem.
(I know this was answered some time ago, but I just ran into this problem and this was my solution. Hopefully it will help anyone new that sees this)
If you are fine with truncating the table of the model in question, you can specify a one-off default value of None in the prompt. The migration will have superfluous default=None while your code has no default. It can be applied just fine because there's no data in the table anymore which would require a default.
If you are in early development cycle and don't care about your current database data you can just remove it and then migrate. But first you need to clean migrations dir and remove its rows from table (django_migrations)
rm your_app/migrations/*
rm db.sqlite3
python manage.py makemigrations
python manage.py migrate
If the SSH it gives you 2 options, choose number 1, and put "None". Just that...for the moment.
One option is to declare a default value for 'new_field':
new_field = models.CharField(max_length=140, default='DEFAULT VALUE')
another option is to declare 'new_field' as a nullable field:
new_field = models.CharField(max_length=140, null=True)
If you decide to accept 'new_field' as a nullable field you may want to accept 'no input' as valid input for 'new_field'. Then you have to add the blank=True statement as well:
new_field = models.CharField(max_length=140, blank=True, null=True)
Even with null=True and/or blank=True you can add a default value if necessary:
new_field = models.CharField(max_length=140, default='DEFAULT VALUE', blank=True, null=True)
I honestly fount the best way to get around this was to just create another model with all the fields that you require and named slightly different. Run migrations. Delete unused model and run migrations again. Voila.
If you are early into the development cycle you can try this -
Remove/comment that model and all its usages. Apply migrations. That would delete that model and then add the model again, run migrations and you have a clean model with the new field added.
In case anyone is setting a ForeignKey, you can just allow nullable fields without setting a default:
new_field = models.ForeignKey(model, null=True)
If you already have data stored within the database, you can also set a default value:
new_field = models.ForeignKey(model, default=<existing model id here>)
If "website" can be empty than new_field should also be set to be empty.
Now if you want to add logic on save where if new_field is empty to grab the value from "website" all you need to do is override the save function for your Model like this:
class UserProfile(models.Model):
user = models.OneToOneField(User)
website = models.URLField(blank=True, default='DEFAULT VALUE')
new_field = models.CharField(max_length=140, blank=True, default='DEFAULT VALUE')
def save(self, *args, **kwargs):
if not self.new_field:
# Setting the value of new_field with website's value
self.new_field = self.website
# Saving the object with the default save() function
super(UserProfile, self).save(*args, **kwargs)
You can't add reference to table that have already data inside.
Change:
user = models.OneToOneField(User)
to:
user = models.OneToOneField(User, default = "")
do:
python manage.py makemigrations
python manage.py migrate
change again:
user = models.OneToOneField(User)
do migration again:
python manage.py makemigrations
python manage.py migrate
In models.py
class UserProfile(models.Model):
user = models.OneToOneField(User)
website = models.URLField(blank=True)
new_field = models.CharField(max_length=140, default="some_value")
You need to add some values as default.
I was early in my development cycle, so this may not work for everyone (but I don't see why it wouldn't).
I added blank=True, null=True to the columns where I was getting the error. Then I ran the python manage.py makemigrations command.
Immediately after running this command (and before running python manage.py migrate), I removed the blank=True, null=True from all the columns. Then I ran python manage.py makemigrations again. I was given an option to just change the columns myself, which I selected.
Then I ran python manage.py migrate and everything worked well!
You can use method from Django Doc from this page https://docs.djangoproject.com/en/1.8/ref/models/fields/#default
Create default and use it
def contact_default():
return {"email": "[email protected]"}
contact_info = JSONField("ContactInfo", default=contact_default)
Source: Stackoverflow.com