Django Generic Foreign keys - Good or Bad considering the SQL performance?

Question

I have a model A which contains a generic foreign key relation with limit choices to 3 other models(consider them as B, C and D) in the same app. And I know the limitations of generic foreign keys that we can't use filter or get or anyother queryset operations.

So to achieve something like this, A.objects.filter(generic_object__name="foo") I have to filter B, C and D's objects first as queryset, iterate over them and use the generic reverse relation to get the A objects as list(not queryset).

I'm not sure about how it'll affect the SQL performace on database as the querying is not direct.

PS: I need to use the generic foreignkeys, so please suggest for any SQL improvement rather than redesigning of models.

Using Django 1.4.3 and Postgres.

Answer 1

I'd like to quote some words from David Cramer: developer of Disqus, Django commiter

Generic relations are fine. They are not slow, just more difficult to manage in your code base.

I saw many people tell others don't use generic relations because it's slow, but never tell how it's slow.