audit system for parent-child tables

Hello list,

I have the need to audit a purchase order process that mainly deals with
PO header and details table, users need to know at any given time how
the purchase order was, like a snapshot, I already log any change to a
separate parallel table.

One way I could do is log each change in both tables a insert in the
audit tables each row in the detail and the row of the header, but that
way could generate a lot of data,

any idea or suggestion to get this done in postgresql ?

Thanks in advance

--
Sinceramente,
Josué Maldonado.

... "El verdadero placer está en la búsqueda, más que en la
explicación." -- Isaac Asimov