Django GenericTabularInline for multiple databases

Question

I've been trying to make the GenericTabularInline class work in a two-admin two-databases setup by inheriting from it and overriding some methods in the BaseModelAdmin class, as is done in the Django docs (https://docs.djangoproject.com/en/dev/topics/db/multi-db/), but if a child model is edited in the inline form, it always writes to the default database (I want the second admin to deal exclusively with a secondary database, models are the same for both), so I must not be overriding some method(s) or doing something wrong. Here's the class I have so far:

class MultiDBGenericTabularInline(generic.GenericTabularInline):

    using = settings.SECONDARY_DATABASE

    def save_model(self, request, obj, form, change):
        # Tell Django to save objects to the 'other' database.
        obj.save(using=self.using)

    def delete_model(self, request, obj):
        # Tell Django to delete objects from the 'other' database
        obj.delete(using=self.using)

    def queryset(self, request):
        # Tell Django to look for objects on the 'other' database.
        return super(MultiDBGenericTabularInline, self).queryset(request).using(self.using)

    def formfield_for_foreignkey(self, db_field, request=None, **kwargs):
        # Tell Django to populate ForeignKey widgets using a query
        # on the 'other' database.
        return super(MultiDBGenericTabularInline, self).formfield_for_foreignkey(db_field, request=request, using=self.using, **kwargs)

    def formfield_for_manytomany(self, db_field, request=None, **kwargs):
        # Tell Django to populate ManyToMany widgets using a query
        # on the 'other' database.
        return super(MultiDBGenericTabularInline, self).formfield_for_manytomany(db_field, request=request, using=self.using, **kwargs)

    #Override these three methods; otherwise the log manager attempts
    #to write to the main db and raises an exception.

    def log_addition(self, request, object):
        pass

    def log_change(self, request, object, message):
        pass

    def log_deletion(self, request, object, object_repr):
        pass

Any help or hints are appreciated.

Answer 1

I realize this is an old question, but I've stumbled across a very similar thing recently. The trick is to override the parent Model Admin's save_formset method. In my case, the solution is to do something like this:

class SomeTabularInline(admin.TabularInline):
    # stuff


class MyModelAdmin(admin.ModelAdmin):
    using = 'something'
    inlines = (SomeTabularInline,)

    def save_formset(self, request, form, formset, change):
        instances = formset.save(commit=False)
        for obj in formset.deleted_objects:
            obj.delete(using=self.using)
        for instance in instances:
            instance.save(using=self.using)
        formset.save_m2m()

Note: I'm using a TabularInline instance, and not a GenericTabularInline but they both descend from InlineModelAdmin; so I'm hopeful that this would work in your case.

Source: https://docs.djangoproject.com/en/1.9/ref/contrib/admin/#django.contrib.admin.ModelAdmin.save_formset