> I'm using Ruby on Rails and have two tables, A and B. Every row in A
> needs a corresponding row in B. A also contains a FK pointing to B.
>
> I created a before insert trigger on A that inserts a new row in B, and
> sets the FK in A. This seems to be running fine.
So, A has a b_id field linking to B ?
If you need a 1-1 relationship, you could try instead to use the same
primary key in B than in A :
A : id SERIAL PRIMARY KEY
B : id INTEGER PRIMARY KEY (not SERIAL)
Then, AFTER INSERT trigger on A checks the value the sequence put in A.id
and inserts in B with this value as the PK.
Postgres has INSERT ... RETURNING which is a very clean and elegant
solution but Rails never heard about it...