#32726: Enforce database level constraints for fields with limited choices
-------------------------------------+-------------------------------------
               Reporter:  eeriksp    |          Owner:  nobody
                   Type:  New        |         Status:  new
  feature                            |
              Component:  Database   |        Version:  dev
  layer (models, ORM)                |       Keywords:  validation database
               Severity:  Normal     |  constraints
           Triage Stage:             |      Has patch:  0
  Unreviewed                         |
    Needs documentation:  0          |    Needs tests:  0
Patch needs improvement:  0          |  Easy pickings:  0
                  UI/UX:  0          |
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 The following is based on PostgresSQL, but is applicable to other
 databases as well.

 When I define a `CharField`, for example this one from the official docs:

 `year_in_school = models.CharField(max_length=2,
 choices=YearInSchool.choices, default=YearInSchool.FRESHMAN)`

 a regular `VARCHAR` field will be defined in the database with no
 constraints preventing me from inserting other strings to it when I
 interact directly with the database bypassing the Django layer.

 This would compromise data integrity and lead to a state where an
 unforeseen string is stored in that field which the application would not
 be able to properly handle.

 To prevent such a inconsistent state, I propose that one of the following
 restrictions would be implemented (the choice might be database specific):
   - add a `CHECK` constraint to the field which would ensure that the
 value falls into the range of acceptable choices
   - use the enum datatype to declare acceptable choices
   - create an auxiliary table to store the acceptable choices and add a
 foreign key constraint to the field

-- 
Ticket URL: <https://code.djangoproject.com/ticket/32726>
Django <https://code.djangoproject.com/>
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