Fast refresh of a materialized view works incorrect

Question

Hi All,
I have created a MV using the sql below:
create materialized view WLS
refresh fast
enable query rewrite
as
SELECT Employees.USER_NAME,
       Permissions.ROLE_NAME,
       Vouchers.VOUCHER_ID,
       EmployeeRoles.FROM_DATE,
       EmployeeRoles.TO_DATE,
       VoucherPatterns.rowid   ACC_VOUCHER_PATTERNS_ROW_ID,
       Vouchers.rowid          ACC_VOUCHERS_ROW_ID,
       Ledgers.rowid           ACC_LEDGERS_ROW_ID,
       Employees.rowid         BANK_EMPLOYEES_ROW_ID,
       IncExcUnits.rowid       INC_EXC_UNITS_ROW_ID,
       EmployeeRoles.rowid     BANK_EMPLOYEE_ROLES_ROW_ID,
       ParentRoles.rowid       PARENT_ROLES_ROW_ID,
       Roles.rowid             ROLES_ROW_ID,
       Permissions.rowid       PERMISSIONS_ROLES_ROW_ID,
       RolesMemberships.rowid  ROLES_MEMBERSHIPS_ROW_ID
  FROM ACC_VOUCHER_PATTERNS        VoucherPatterns,
       ACC_VOUCHERS                Vouchers,
       ACC_LEDGERS                 Ledgers,
       BANK_EMPLOYEES              Employees,
       BANK_EMPLOYEE_INC_EXC_UNITS IncExcUnits,
       BANK_EMPLOYEE_ROLES         EmployeeRoles,
       ROLES                       ParentRoles,
       ROLES                       Roles,
       ROLES                       Permissions,
       ROLES_MEMBERSHIPS           RolesMemberships
WHERE Vouchers.TYPE_VOUCHER_PATTERN_FK =
       VoucherPatterns.VOUCHER_PATTERN_ID
   AND VoucherPatterns.CONFIRM_COUNT = 2
   AND Vouchers.STATE = 'ISU'
   AND Vouchers.LEDGER_FK = Ledgers.LEDGER_ID
   AND Employees.ID = IncExcUnits.BKEM_ID(+)
   AND (((IncExcUnits.INC_EXCLUD_TYPE IS NULL OR
       IncExcUnits.INC_EXCLUD_TYPE != 'EXC') AND
       Ledgers.ORGANIZATION_UNIT_FK = Employees.ORGU_ID) OR
       (Ledgers.ORGANIZATION_UNIT_FK = IncExcUnits.ORGU_ID AND
       IncExcUnits.INC_EXCLUD_TYPE = 'INC'))
   AND EmployeeRoles.BKEM_ID = Employees.ID
   AND ParentRoles.ID = EmployeeRoles.ROLS_ID
   AND ParentRoles.IS_PERMISSION = 'N'
   AND ParentRoles.ROLE_TYPE = 'ORG'
   AND ParentRoles.ID = Roles.ROLS_ID
   AND Roles.IS_PERMISSION = 'N'
   AND Roles.ROLE_TYPE = 'SYS'
   AND Permissions.IS_PERMISSION = 'Y'
   AND Permissions.ROLE_NAME = 'ACC_AccVoucherConfirm'
   AND Roles.ID = RolesMemberships.ROLS_ID
   AND Permissions.ID = RolesMemberships.ROLS_ID_MEMBER_OF;
Then I have issued a SELECT * though it and that works fine.
And then I've manipulated the data in some tables such that according to MV's WHERE clause it must return no rows.
Intuitively before refreshing the MV it will return the data last placed on it,
But it return the same data after issuing the following command in PL/SQL Developer:
call dbms_mview.refresh(list => 'WLS', method => 'F');
And unfortunately the following will correct it:
call dbms_mview.refresh(list => 'WLS', method => 'C');
Why the fast refresh of a fast refreshable MV does not work fine while its complete refresh works good?
How ever after undoing made changes to those tables and issuing the fast refresh using the following command the MV will contain correct updated data:
call dbms_mview.refresh(list => 'WLS', method => 'F');
It seems that it has bug in deleting rows from Fast Refreshable MV but upserts work fine.
I've tried to simulate the problem for a simpler query with simple tables containing some sample data but those don't have any problem.
Please help me,
Thanks

Answer 1

Thanks Martin,
Finally I've discovered one of possible several situations in which a MV fast refreshed incorrectly.
This is happened when an OR condition exists among several AND conditions and at least one outer join symbol there exists!
this is the scenario:
-- create two sample tables
create table t as select 1 a, 2 b from dual;
create table j as select 1 a, 2 b from dual;
-- defining primary keys
alter table t add constraint tp primary key (a);
alter table j add constraint jp primary key (a);
-- creating MV Logs
create materialized view log on t with primary key, rowid;
create materialized view log on j with primary key, rowid;
-- creating Fast Refresh MV with a sample query
create materialized view mvt refresh fast enable query rewrite as
select t.a, j.b, t.rowid tr, j.rowid jr from t,j where t.a = j.a(+)
and (t.b = j.b or t.a = t.b);
-- select through MV, the MV returns correct data
select * from mvt;
     A    B    TR                    JR
    1    2    AAAYwQAAEAAFhwzAAA    AAAYwRAAEAAFhw7AAA
-- intentionally manipulate the data to the query returns no rows
update j set a = 2;
commit;
-- query the select of MV
select t.a, j.b, t.rowid tr, j.rowid jr from t,j where t.a = j.a(+)
and (t.b = j.b or t.a = t.b);
-- returns now rows, The query rewrite does not work here!
-- select through MV, the MV returns correct data because it has not refreshed yet!
select * from mvt;
     A    B    TR                    JR
    1    2    AAAYwQAAEAAFhwzAAA    AAAYwRAAEAAFhw7AAA
-- fast refreshing the mv and issuing select again
call dbms_mview.refresh(list => 'MVT', method => 'F');
select * from mvt;
     A    B        TR                    JR
    1    null    AAAYwuAAEAAFh2jAAA    null
-- A change is occured but it is not correct, it must returns no rows!
-- query the select of MV
select t.a, j.b, t.rowid tr, j.rowid jr from t,j where t.a = j.a(+)
and (t.b = j.b or t.a = t.b);
     A    B        TR                    JR
    1    null    AAAYwuAAEAAFh2jAAA    null
-- Query rewrite does work here! because appending a neutral "and 1=1" conditions will show the correct empty result:
select t.a, j.b, t.rowid tr, j.rowid jr from t,j where t.a = j.a(+)
and (t.b = j.b or t.a = t.b) and 1=1;
-- returns no rows
-- now complete refreshing the MV and achieving the correct result:
call dbms_mview.refresh(list => 'MVT', method => 'C');
select * from mvt;
-- returns no rows
Is this a BUG?
Any suggestions?