Django models: default value for column

Question

I have following Django model code:

status = models.PositiveIntegerField(default = 0b000)
comments_allowed = models.BooleanField(default = True)         


        

Answer 1

Note that the default parameter can also take a callable object: https://docs.djangoproject.com/en/dev/ref/models/fields/#default. That is certainly a behavior that cannot be reproduced in SQL! So it would not be possible for Django to generate SQL for every possible case. It looks like for the sake of simplicity and consistency they have chosen not to generate SQL for any case.

Answer 2

It seems that django has supported the default parameters in MySQL 8.0.13+. Fixed #30712 -- Allowed BLOB/TEXT defaults on MySQL 8.0.13+.

Answer 3

The only permanent solution is to patch the Django source, specifically db/backends/creation.py:

Find:

if f.primary_key:
    field_output.append(style.SQL_KEYWORD('PRIMARY KEY'))
elif f.unique:
    field_output.append(style.SQL_KEYWORD('UNIQUE'))

After add:

if(f.default != models.fields.NOT_PROVIDED):
    field_output.append(style.SQL_KEYWORD('DEFAULT ' + str(f.default)))

(Source: http://www.supermind.org/blog/671/django-not-setting-default-column-value-in-mysql)

Alternatively (and preferably), if you're using South, you can just execute some additional SQL after the db.create_table in your migration:

MySQL:

db.execute("ALTER TABLE yourapp_yourmodel MODIFY status int Default '4'")

Postgres:

db.execute("ALTER TABLE yourapp_yourmodel ALTER COLUMN status SET DEFAULT 4")

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