Django Polymorphic
Polymorphic Django model inheritance
django-polymorphic improves model inheritance for Django: querying a base model returns instances of the right subclass automatically, instead of the plain base rows Django gives you by default. It’s a widely-used community library (around 1,800 stars), and the use case that pulled me into it was a bug in how Django deleted polymorphic objects.
Django’s delete Collector assumed every model in a delete batch matched the first one, so
deleting across a polymorphic hierarchy could generate the wrong DELETE statements and
raise integrity errors. My patch on ticket #16128 became the basis for the fix in #23076,
which the Django maintainers applied “directly based on a patch submitted by Kronuz.” It’s a
small, sharp kind of contribution I like: a subtle correctness bug in code that thousands of
projects rely on, fixed once, upstream.