conn scott/tiger

create table names(c1 varchar2(10));

begin for i in 1..1000 loop
insert into names values('TIGER');
end loop;
end;
/

insert into names values('SCOTT');

exec dbms_stats.gather_table_stats(user,'names',method_opt=>'for all columns size skewonly');

set autot on exp

select count(*) from names where c1='SCOTT';
select count(*) from names where c1='TIGER';
select count(*) from names where c1=sys_context('userenv','current_user');

orclz>
orclz> create or replace function vpdfunc
  2  (object_schema varchar2,
  3  object_name varchar2)
  4  return varchar2
  5  as
  6  retval varchar2(10);
  7  begin
  8  retval := sys_context('userenv','current_user');
  9  return 'c1 = '||''''|| retval||'''';
 10  end;
 11  /

Function created.

orclz> select vpdfunc('a','b') from dual;

VPDFUNC('A','B')
----------------------------------------------------------------------------------
c1 = 'SCOTT'


Execution Plan
----------------------------------------------------------
Plan hash value: 1388734953

-----------------------------------------------------------------
| Id  | Operation        | Name | Rows  | Cost (%CPU)| Time     |
-----------------------------------------------------------------
|   0 | SELECT STATEMENT |      |     1 |     2   (0)| 00:00:01 |
|   1 |  FAST DUAL       |      |     1 |     2   (0)| 00:00:01 |
-----------------------------------------------------------------

orclz> exec dbms_rls.add_policy('SCOTT','NAMES','P1','SCOTT','VPDFUNC');

PL/SQL procedure successfully completed.

orclz> select count(*) from names;

       COUNT(*)
---------------
              1


Execution Plan
----------------------------------------------------------
Plan hash value: 1341785398

----------------------------------------------------------------------------
| Id  | Operation          | Name  | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |       |     1 |     6 |     3   (0)| 00:00:01 |
|   1 |  SORT AGGREGATE    |       |     1 |     6 |            |          |
|*  2 |   TABLE ACCESS FULL| NAMES |     1 |     6 |     3   (0)| 00:00:01 |
----------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - filter("C1"='SCOTT')

orclz>