If i have a table and a defined policy on it then do I need to redefine the policy if I drop and recreate the table or alter it, provided that the alteration or the recreation of the table does not alter elements that the function needs to see?
"do I need to redefine the policy if I drop and recreate the table"
Yes. Let's create a policy.
SQL> exec dbms_rls.add_policy('APC', 'T23', 'DEPTPOL', 'APC', 'security_policies.get_deptno_predicate')
PL/SQL procedure successfully completed.
SQL> select count(*) from user_policies;
COUNT(*)
----------
1
SQL> exec security_policies.set_deptno(20)
PL/SQL procedure successfully completed.
SQL> select count(*) from t23;
COUNT(*)
----------
6
SQL>
so that works. But if we drop and re-create the table (using a backup I prepared earlier) ...
SQL> drop table t23
2 /
Table dropped.
SQL> create table t23 as select * from t23a
2 /
Table created.
SQL> select count(*) from t23;
COUNT(*)
----------
11
SQL> exec security_policies.set_deptno(20)
PL/SQL procedure successfully completed.
SQL> select count(*) from t23;
COUNT(*)
----------
11
SQL> SQL> select count(*) from user_policies;
COUNT(*)
----------
0
SQL>
"So the question is if I must redefine the policy even if I will not change anything in the definition."
No. Providing the change doesn't invalidate the generated predicate altering a table doesn't drop the policy:
SQL> exec dbms_rls.add_policy('APC', 'T23', 'DEPTPOL', 'APC', 'security_policies.get_deptno_predicate')
PL/SQL procedure successfully completed.
SQL> alter table t23 modify deptno number(3,0)
2
SQL> desc t23
Name Null? Type
----------------------------------------- -------- ----------------------------
NAME VARCHAR2(12 CHAR)
ID NUMBER
AGE NUMBER(4)
DEPTNO NUMBER(2)
SQL> alter table t23 modify deptno number(3,0)
2 /
Table altered.
SQL> exec security_policies.set_deptno(20)
PL/SQL procedure successfully completed.
SQL> select count(*) from t23;
COUNT(*)
----------
6
SQL>
Note that the change modified the column which is tested by the predicate and the policy still remains in force.
"does a 'CREATE OR REPLACE VIEW' statement drops and recreates it or does it alter it?"
Let's try it:
SQL> create view v23 as select * from t23;
View created.
SQL> exec dbms_rls.add_policy('APC', 'V23', 'DEPTPOLV', 'APC', 'security_policies.get_deptno_predicate')
PL/SQL procedure successfully completed.
SQL> exec security_policies.set_deptno(10)
PL/SQL procedure successfully completed.
SQL> select count(*) from v23;
COUNT(*)
----------
5
SQL> create or replace view v23 as select name, age from t23;
View created.
SQL> select count(*) from v23;
select count(*) from v23
*
ERROR at line 1:
ORA-28113: policy predicate has error
SQL>
Okay, so that's an error because the view's new projection doesn't include the column in the predicate. But it suggests teh ploicy is still in place. So let's fix that error:
SQL> create or replace view v23 as select name, age, deptno from t23;
View created.
SQL> select count(*) from v23;
COUNT(*)
----------
5
SQL>