Example:
Given a model with a compressed field named content:
>>> m = MyModel.objects.last()
>>> m.id
123
>>> m.content
'abc'
>>> len(list(MyModel.objects.filter(content=m.content)))
0
That should be at least 1, not 0.
These still work though, as documented:
>>> len(list(MyModel.objects.filter(content__in=[m.content])))
1
>>> len(list(MyModel.objects.filter(content__startswith=m.content)))
1