Oracle 11g function based columns - deterministic function or not?

Question

Hi all, here is my situation:
I added function based column in my table and created index on this column.
I need this since in my ADF application, I need to be able to sort by this column.
The function (that this column is based on) I had to make it DETERMINISTIC (otherwise it can not be done).
So far so good.
My function is accepting 3 parameters (all NUMBERs) which are practically 3 primary keys from 3 different tables. Based on which key is present, my function is returning "Code" - column (VARCHAR2) from any of those 3 tables. And for sure "Code" can change in any of those table.
So my function is not really a DETERMINISTIC function.
-Should I update the function and make it nondeterministic? Will it still work? Will the index be valid if the function is nondeterministic?
-What is the consequence if it is not deterministic?
-If I leave i as deterministic - somehow the result is cached. Will my function always going to be re-executed for each row (having on mind it is not really deterministic)?
-Is there better solution than (function based column and index on it) in my case?
Thanks, Vesna

Answer 1

OK, Damorgan, here are some more details:
Versin Numbers:
Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Production
PL/SQL Release 11.1.0.7.0 - Production
TABLE:
alter table MY_VIRTUAL_COLUMN add dispatch_customer_name  GENERATED ALWAYS AS (get_dispatch_customer_name(disloc_id, cus_id, cusloc_id)) VIRTUAL;
create index dispatch_customer_name_i on MY_VIRTUAL_COLUMN(dispatch_customer_name);FUNCTION:
CREATE OR REPLACE FUNCTION get_dispatch_customer_name(p_disloc_id NUMBER,
                                                      p_cus_id    NUMBER,
                                                      p_cusloc_id NUMBER)
   RETURN VARCHAR2 DETERMINISTIC IS
   v_result VARCHAR2(1000) := NULL;
BEGIN
   IF p_cus_id IS NULL THEN
      IF p_cusloc_id IS NULL THEN
         SELECT d.name
           INTO v_result
           FROM dispatch_locations d
          WHERE d.disloc_id = p_disloc_id;
      ELSE
         SELECT l.name || ' (' || l.code || ')'
           INTO v_result
           FROM customer_locations l
          WHERE l.cusloc_id = p_cusloc_id;
      END IF;
   ELSE
      SELECT s.name || ' (' || s.code || ')'
        INTO v_result
        FROM customers s
       WHERE s.cus_id = p_cus_id;
   END IF;
   RETURN v_result;
EXCEPTION
   WHEN OTHERS THEN
      RETURN NULL;
END get_dispatch_customer_name;Hope this will help
Thanks, Vesna