Need help in how to....

Hi,
   I doing a log to my DB. For this, I writing a trigger that inserts in a
log table the user, date, table changed and values changed.
   I was trying to do a generic procedure and use it on all tables, like 
this:

create function sp_log() returns opaque as '
declare   v_type text;   v_taable text;   v_oid text;   v_old text;   v_new text;
begin   v_type := tg_op;   v_table := tg_relname;   v_oid := tg_relid;   -- v_old := old::text;   -- v_new :=
new::text;  insert into log (tablechanged, action, old_values, new_values, user)       values (v_tabela, v_tipo, v_old,
v_new,current_user);   return new;
 
end;' language 'plpgsql';
   How I do to get the old and new values in a generic way (without use
coluns names or any else that bind a specific table)?
   Thanks for all help,
   Edipo Elder   [edipoelder@ig.com.br]

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