function f_client_exists_device_model(client_id int, device_model_id int) returns boolean
     as
     declare variable tmp int;
     begin
       select first 1 sp.ID
       from devices d
       left join SP_DEVICE_MODEL_TREE(d.model_id) sp on 1=1
       where d.client_id = :client_id and d.is_actual
             and sp.id = :device_model_id
       into :tmp;

       return (tmp is not null);
     end