Specifying a mySQL ENUM in a Django model

By : Steve
Source: Stackoverflow.com
Question!

How do I go about specifying and using an ENUM in a Django model?

By : Steve


Answers

From the Django documentation:

MAYBECHOICE = (
    ('y', 'Yes'),
    ('n', 'No'),
    ('u', 'Unknown'),
)

And you define a charfield in your model :

married = models.CharField(max_length=1, choices=MAYBECHOICE)

You can do the same with integer fields if you don't like to have letters in your db.

In that case, rewrite your choices:

MAYBECHOICE = (
    (0, 'Yes'),
    (1, 'No'),
    (2, 'Unknown'),
)


Using the choices parameter won't use the ENUM db type; it will just create a VARCHAR or INTEGER, depending on whether you use choices with a CharField or IntegerField. Generally, this is just fine. If it's important to you that the ENUM type is used at the database level, you have three options:

  1. Use "./manage.py sql appname" to see the SQL Django generates, manually modify it to use the ENUM type, and run it yourself. If you create the table manually first, "./manage.py syncdb" won't mess with it.
  2. If you don't want to do this manually every time you generate your DB, put some custom SQL in appname/sql/modelname.sql to perform the appropriate ALTER TABLE command.
  3. Create a custom field type and define the db_type method appropriately.

With any of these options, it would be your responsibility to deal with the implications for cross-database portability. In option 2, you could use database-backend-specific custom SQL to ensure your ALTER TABLE is only run on MySQL. In option 3, your db_type method would need to check the database engine and set the db column type to a type that actually exists in that database.

UPDATE: Since the migrations framework was added in Django 1.7, options 1 and 2 above are entirely obsolete. Option 3 was always the best option anyway. The new version of options 1/2 would involve a complex custom migration using SeparateDatabaseAndState -- but really you want option 3.



There're currently two github projects based on adding these, though I've not looked into exactly how they're implemented:

  1. Django-EnumField:
    Provides an enumeration Django model field (using IntegerField) with reusable enums and transition validation.
  2. Django-EnumFields:
    This package lets you use real Python (PEP435-style) enums with Django.

I don't think either use DB enum types, but they are in the works for first one.



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