COcollinmanderson·Nov 22, 2021
:)
Django currently requires that every table have a _single_ primary key column. You can have a unique multi-column index, but you _also_ need to have a single primary key column, which sometimes makes working with existing databases tricky or inefficient.
It's Django's oldest open ticket, from August 2005: https://code.djangoproject.com/ticket/373
The trick is how do you group those columns together in a way that stays compatible with the rest of the framework.
Here's a 2015 proposal "DEP 191" for how to make it work:
- https://github.com/django/deps/blob/main/draft/0191-composit...
Basically, the multi-columns end up needing to be exposed as a single python object (CompositeField) to stay compatible with the rest of the framework, but do changes to the individual "subfields" on the row-object need to be kept in sync (data binding) with
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the CompositeField-object and maybe vice-versa? Now we need an "Observer" (which Django doesn't currently have) to watch for changes to fields, etc. So a lot of new concepts end up needing to be introduced to make this happen. And it needs to work with migrations and serialization while trying to maintain backward-compatibility.
Here's rough code (again, from 2015):
https://github.com/django/django/pull/4553
Since 2015, Django now has class-based-indexes which should make things slightly easier:
https://docs.djangoproject.com/en/stable/ref/models/indexes/
Maybe at least the Observables could get merged in as a first-step which would make the remaining work a little easier?