How to update a unique field in ModelAdmin with a non-unique value on bulk data update?

Question

Django

There is a model with a unique field filled with unique values.

class MyModel(models.Model):
    uniqfield = models.IntegerField('Уникальное поле', unique=True)

The admin panel has a class inherited from ModelAdmin for editing this model.

@admin.register(MyModel)
class MyModelAdmin(admin.ModelAdmin):
    list_display = ('uniqfield',)
    
    def save_model(self, request, obj, form, change):
        try:
            obj.save()
        except
            # соообщение об не уникальности вставляемых значений

I want to simultaneously change, for example, two values ​​in this field to each other. For example:

pk=1, uniqfield=1
pk=2, uniqfield=2

я в форме редактирования на странице меняю их местами и хочу получить:
pk=1, uniqfield=2
pk=2, uniqfield=1

obj.save() throws a predictable exception due to non-unique values, i.e. when you update the first value in the table, it is still present.

How to do it?

Answer 1

1. hands pk=1 to assign 3, pk=2 to assign 1, pk=1 to assign 2
2. write admin action not to do it manually
PS exclude null from uniqueness and then it can be used instead of 3.