Virtual Private Database (VPD) aka Fine Grained Access Control may seem complicated at first when you look at the fine documentation about it.
This article gives a short and simple example to get you started easily. The demo below is with 12c Multitenant but works the same with 11g:
SQL> connect reports_owner/reports_owner@pdb1 Connected. SQL> select * from reports_table; REPORT_NAME F ------------------------------ - Monthly report R1 M Monthly report R2 M Daily report R1 D Daily report R2 D SQL> grant create session to monthly identified by monthly; Grant succeeded. SQL> grant select on reports_table to monthly; Grant succeeded. SQL> grant create session to daily identified by daily; Grant succeeded. SQL> grant select on reports_table to daily; Grant succeeded.
Say this is a reporting system with a central table that is used for monthly and daily reports. We have separate users for the daily and monthly reports.
Initially, they see both kinds of entries in the table:
SQL> connect monthly/monthly@pdb1 Connected. SQL> select * from reports_owner.reports_table; REPORT_NAME F ------------------------------ - Monthly report R1 M Monthly report R2 M Daily report R1 D Daily report R2 D SQL> connect daily/daily@pdb1 Connected. SQL> select * from reports_owner.reports_table; REPORT_NAME F ------------------------------ - Monthly report R1 M Monthly report R2 M Daily report R1 D Daily report R2 D
VPD enables both users to keep the same statement but they see only rows for monthly respectively daily frequency:
SQL> connect reports_owner/reports_owner@pdb1
Connected.
SQL> create or replace function frequency_function (schema varchar2, tab varchar2)
return varchar2
is
who varchar2(20);
freq char(1);
begin
select sys_context('userenv','session_user') into who from dual;
case who
when 'MONTHLY' then freq:='M';
when 'DAILY' then freq:='D';
else freq:='?';
end case;
return 'frequency=''' || freq || '''';
end;
/
Function created.
SQL> begin
dbms_rls.add_policy(
object_schema=>'REPORTS_OWNER',
object_name=>'REPORTS_TABLE',
policy_name=>'FREQUENCY_POLICY',
function_schema=>'REPORTS_OWNER',
policy_function=>'frequency_function');
end;
/
PL/SQL procedure successfully completed.
SQL> connect monthly/monthly@pdb1
Connected.
SQL> select * from reports_owner.reports_table;
REPORT_NAME F
------------------------------ -
Monthly report R1 M
Monthly report R2 M
SQL> connect daily/daily@pdb1
Connected.
SQL> select * from reports_owner.reports_table;
REPORT_NAME F
------------------------------ -
Daily report R1 D
Daily report R2 D
This is possible because VPD silently attaches a WHERE condition to the seemingly unchanged statement:
SQL> connect sys/oracle@pdb1 as sysdba
Connected.
SQL> grant select_catalog_role to monthly;
Grant succeeded.
SQL> connect monthly/monthly@pdb1
Connected.
SQL> select * from reports_owner.reports_table;
REPORT_NAME F
------------------------------ -
Monthly report R1 M
Monthly report R2 M
SQL> select plan_table_output from table(dbms_xplan.display_cursor);
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------
SQL_ID 16xw6bqhp67gw, child number 0
-------------------------------------
select * from reports_owner.reports_table
Plan hash value: 2149466028
-----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 3 (100)| |
|* 1 | TABLE ACCESS FULL| REPORTS_TABLE | 2 | 38 | 3 (0)| 00:00:01 |
-----------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("FREQUENCY"='M')
18 rows selected.
The VPD policy adds that WHERE condition depending on the session user. Funny effect:
SQL> connect reports_owner/reports_owner@pdb1
Connected.
SQL> select * from reports_table;
no rows selected
SQL> select plan_table_output from table(dbms_xplan.display_cursor);
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------
SQL_ID 8xc692y0axx0x, child number 0
-------------------------------------
select * from reports_table
Plan hash value: 2149466028
-----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 3 (100)| |
|* 1 | TABLE ACCESS FULL| REPORTS_TABLE | 1 | 19 | 3 (0)| 00:00:01 |
-----------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("FREQUENCY"='?')
18 rows selected.
SYS is not subject to this policy, because of his privilege EXEMPT ACCESS POLICY:
SQL> connect sys/oracle@pdb1 as sysdba Connected. SQL> select * from reports_owner.reports_table; REPORT_NAME F ------------------------------ - Monthly report R1 M Monthly report R2 M Daily report R1 D Daily report R2 D SQL> grant exempt access policy to reports_owner; Grant succeeded. SQL> connect reports_owner/reports_owner@pdb1 Connected. SQL> select * from reports_table; REPORT_NAME F ------------------------------ - Monthly report R1 M Monthly report R2 M Daily report R1 D Daily report R2 D SQL> select plan_table_output from table(dbms_xplan.display_cursor); PLAN_TABLE_OUTPUT ------------------------------------------------------------------------------------------------------------------------------------------------------ SQL_ID 8xc692y0axx0x, child number 1 ------------------------------------- select * from reports_table Plan hash value: 2149466028 ----------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ----------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 3 (100)| | | 1 | TABLE ACCESS FULL| REPORTS_TABLE | 4 | 76 | 3 (0)| 00:00:01 | ----------------------------------------------------------------------------------- 13 rows selected.
So much for starters. Things get more complicated especially if there are no different database users as in the above simplified example. That is usually where an application context is being used – but that could be a topic for another article 🙂
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