A doubt about table partitioning. (Item 5.9 from Postgresql online manual)

My Best Regards to all on this Mail List...

I'm using table partition on a large database to improve query performance 
and vacuum management.
I'm read and understand all in item 5.9 in postgresql online manual.

In my father table, I have all the columns needed and which one is primary 
key and have a sequence (nextval() funcion as default value of then) 
associated.
On other tables (not inherited from this) I need to have Foreing keys 
pointing to this table.
My doubt and preocupation is about FK check becouse I don't know if 
PostgreSQL will make a seq scan on all child tables (inherited) to found 
values, becouse the primary key index is located into father table.
I will have a great problem in FK check if seq scan occurs, becouse my 
father table will take a billion of rows or more.

Is there any other way to solute this? I think the suggested in postgresql 
manual's items 5.9.2-5.9.4 are not useful for this case.

Thanks...

Lucio