python - Altering unique fields of inherited Django model -

in django, i'm trying create base model can used track different version of other model's data in transparent way. like:

class warehouse(models.model):      version_number = models.integerfield()     objects = custommodelmanagerfilteringonversionnumber()      class meta:         abstract=true      def save(self, *args, **kwargs):         # handling here version number incrementation         # never overwrite data create separate records,         # don't delete mark deleted, etc.         pass  class somedata(warehouse):     id = models.integerfield( primary_key=true )     name = models.charfield(unique=true) 

the problem have somedata.name not unique, tuple ('version_number', 'name' ) is.

i know can use meta class in somedata unique_together wondering whether done in more transparent way. is, dynamically modifying/creating unique_together field.

final note: maybe handling model inheritance not correct approach looked pretty appealing me if can handle field uniqueness problem.

edit: word 'dynamic' in context misleading. want uniqueness preserved @ database level. idea have different version of data.

a give here small example above model (assuming abstract model inheritance, in same table):

the database contain:

 version_number | id | name  | #comment 0              | 1  | bob   | first insert 0              | 2  | nicky | first insert 1              | 1  | bobby | bob changed name on day x.y.z 0              | 3  | malcom| first insert 1              | 3  | malco | name change 2              | 3  | momo  | again... 

and custom model manager filter data (taking max on version number every unique id) that: somedata.objects.all() return

 id | name 1  | bobby 2  | nicky 3  | momo 

and offer others method can return data in version n-1.

obviously use timestamp instead of version number can retrieve data @ given date principle remains same.

now problem when ./manage.py makemigrations models above, enforce uniqueness on somedata.name , on somedata.id when need uniqueness on ('somedata.id','version_number') , ('somedata.name', 'version_number'). explicitly, need append fields base models fields of inherited models declared unique in db , times manage.py command run and/or production server runs.

by "dynamically modifying/creating unique_together field", assume mean want enforce @ code level, not @ database level.

you can in save() method of model:

from django.core.exceptions import validationerror  def save(self, *args, **kwargs):     if somedata.objects.filter(name=self.name, version_number=self.version_number).exclude(pk=self.pk).exists():         raise validationerror('such thing exists')      return super(somedata, self).save(*args, **kwargs) 

hope helps!