SELECT REMAP_STR_FUNC(COL1),REMAP_NUMBER_FUNC(COL2),REMAP_DATE_FUNC(COL3),... FROM TABLE_WITH_10_MILLION_ROWS;

CREATE OR REPLACE
  FUNCTION null_sensitive_data(
                               p_owner IN VARCHAR2,
                               p_name  IN VARCHAR2
                              )
    RETURN VARCHAR2 AS
    BEGIN
        RETURN 'USER != ''U1''';
END;
/
BEGIN
  DBMS_RLS.ADD_POLICY (
                       object_schema         => 'SCOTT',
                       object_name           => 'EMP',
                       policy_name           => 'null_sensitive_data_rls',
                       function_schema       => 'SCOTT',
                       policy_function       => 'null_sensitive_data',
                       policy_type           => DBMS_RLS.STATIC,
                       sec_relevant_cols     => 'SAL,COMM',
                       sec_relevant_cols_opt => DBMS_RLS.ALL_ROWS
                      );
END;
/

SQL> SHOW USER
USER is "U2"
SQL> SELECT  *
  2    FROM  SCOTT.EMP
  3  /

EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
----- ---------- --------- ---------- --------- ---------- ---------- ----------
 7369 SMITH      CLERK           7902 17-DEC-80        800                    20
 7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
 7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
 7566 JONES      MANAGER         7839 02-APR-81       2975                    20
 7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
 7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
 7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
 7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
 7839 KING       PRESIDENT            17-NOV-81       5000                    10
 7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
 7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
 7900 JAMES      CLERK           7698 03-DEC-81        950                    30
 7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
 7934 MILLER     CLERK           7782 23-JAN-82       1300                    10

14 rows selected.

SQL>
...
SQL> SHOW USER
USER is "U1"
SQL> SELECT  *
  2    FROM  SCOTT.EMP
  3  /

EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
----- ---------- --------- ---------- --------- ---------- ---------- ----------
 7369 SMITH      CLERK           7902 17-DEC-80                               20
 7499 ALLEN      SALESMAN        7698 20-FEB-81                               30
 7521 WARD       SALESMAN        7698 22-FEB-81                               30
 7566 JONES      MANAGER         7839 02-APR-81                               20
 7654 MARTIN     SALESMAN        7698 28-SEP-81                               30
 7698 BLAKE      MANAGER         7839 01-MAY-81                               30
 7782 CLARK      MANAGER         7839 09-JUN-81                               10
 7788 SCOTT      ANALYST         7566 19-APR-87                               20
 7839 KING       PRESIDENT            17-NOV-81                               10
 7844 TURNER     SALESMAN        7698 08-SEP-81                               30
 7876 ADAMS      CLERK           7788 23-MAY-87                               20
 7900 JAMES      CLERK           7698 03-DEC-81                               30
 7902 FORD       ANALYST         7566 03-DEC-81                               20
 7934 MILLER     CLERK           7782 23-JAN-82                               10

14 rows selected.

SQL>