Regarding RULE Hint Removal

Question

Hi ..
We have an application having 40+ SQL's using RULE Hint. (11g R2).
Now we have a plan to upgrade to 12c and we want to come out of these RULE Hints.
Anyone faced similar kind of issue? what are do's and don't do's to remove RULE Hint. Please advise.
Thank you!
Regards
Siva
Edited by: 985936 on Feb 4, 2013 3:33 AM

Answer 1

It looks like the /*+ RULE */ hint can still have an impact in 11.2.0.3:
07:23:12 SQL> select * from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
PL/SQL Release 11.2.0.3.0 - Production
CORE    11.2.0.3.0      Production
TNS for Solaris: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production
5 rows selected.
Elapsed: 00:00:00.04
07:23:20 SQL> create table test_rule_optimizer  as select * from dba_objects;
Table created.
Elapsed: 00:00:03.04
07:23:23 SQL> create index TEST_RULE_OPTIMIZER_IDX on TEST_RULE_OPTIMIZER(object_type, owner, object_name);
Index created.
Elapsed: 00:00:01.32
07:23:24 SQL>
07:23:24 SQL> begin
07:23:25   2    dbms_stats.gather_table_stats(ownname => user, tabname => 'TEST_RULE_OPTIMIZER');
07:23:25   3  end;
07:23:25   4  /
PL/SQL procedure successfully completed.
Elapsed: 00:00:03.91
07:23:29 SQL>
07:23:45 SQL> set autotrace on
07:23:45 SQL> --
07:23:45 SQL> -- Choosing these object types because they comprise over 50% of the objects in my table
07:23:45 SQL> select count(*), max(last_ddl_time)
07:23:45   2  from TEST_RULE_OPTIMIZER
07:23:45   3  where object_type in ('INDEX','SYNONYM','INDEX PARTITION','LOB PARTITION');
  COUNT(*) MAX(LAST_DDL_TIME)
    136189 2013/02/04 04:17:04
1 row selected.
Elapsed: 00:00:00.12
Execution Plan
Plan hash value: 166585403
| Id  | Operation          | Name                | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT   |                     |     1 |    19 |  1078   (2)| 00:00:01 |
|   1 |  SORT AGGREGATE    |                     |     1 |    19 |            |          |
|*  2 |   TABLE ACCESS FULL| TEST_RULE_OPTIMIZER | 19721 |   365K|  1078   (2)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - filter("OBJECT_TYPE"='INDEX' OR "OBJECT_TYPE"='INDEX PARTITION' OR
              "OBJECT_TYPE"='LOB PARTITION' OR "OBJECT_TYPE"='SYNONYM')
Statistics
          1  recursive calls
          0  db block gets
       3850  consistent gets
          0  physical reads
          0  redo size
        275  bytes sent via SQL*Net to client
        248  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed
07:23:46 SQL>
07:23:46 SQL> select /*+ rule */ count(*), max(last_ddl_time)
07:23:46   2  from TEST_RULE_OPTIMIZER
07:23:46   3  where object_type in ('INDEX','SYNONYM','INDEX PARTITION','LOB PARTITION');
  COUNT(*) MAX(LAST_DDL_TIME)
    136189 2013/02/04 04:17:04
1 row selected.
Elapsed: 00:00:00.29
Execution Plan
Plan hash value: 316642056
| Id  | Operation                     | Name                    |
|   0 | SELECT STATEMENT              |                         |
|   1 |  SORT AGGREGATE               |                         |
|   2 |   CONCATENATION               |                         |
|   3 |    TABLE ACCESS BY INDEX ROWID| TEST_RULE_OPTIMIZER     |
|*  4 |     INDEX RANGE SCAN          | TEST_RULE_OPTIMIZER_IDX |
|   5 |    TABLE ACCESS BY INDEX ROWID| TEST_RULE_OPTIMIZER     |
|*  6 |     INDEX RANGE SCAN          | TEST_RULE_OPTIMIZER_IDX |
|   7 |    TABLE ACCESS BY INDEX ROWID| TEST_RULE_OPTIMIZER     |
|*  8 |     INDEX RANGE SCAN          | TEST_RULE_OPTIMIZER_IDX |
|   9 |    TABLE ACCESS BY INDEX ROWID| TEST_RULE_OPTIMIZER     |
|* 10 |     INDEX RANGE SCAN          | TEST_RULE_OPTIMIZER_IDX |
Predicate Information (identified by operation id):
   4 - access("OBJECT_TYPE"='LOB PARTITION')
   6 - access("OBJECT_TYPE"='INDEX PARTITION')
   8 - access("OBJECT_TYPE"='SYNONYM')
  10 - access("OBJECT_TYPE"='INDEX')
Note
   - rule based optimizer used (consider using cbo)
Statistics
          1  recursive calls
          0  db block gets
      37884  consistent gets
          3  physical reads
          0  redo size
        276  bytes sent via SQL*Net to client
        248  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed
07:23:46 SQL>
07:23:47 SQL>