Index is not getting picked even after providing hint

Question

Hi All
The index pk_sku is not getting picked even after providing the hints when executing the query.Please kindly give me such recommendations.I am providing the information.
select  * from
(select /*+ index(s pk_sku) */
      to_char(t.dstamp, 'YYYYmmDDHH24MI') as sort_1,
      t.client_id as CLIENT_ID ,
      t.site_id as SITE_ID,
      tz.time_zone_name as TIME_ZONE_NAME     ,
      t.owner_id as OWNER_ID,
      t.sku_id as SKU_ID,
      t.reason_id as ADJUST_TYPE,
      to_char(t.dstamp+tz.diff/24, 'DD/mm/YYYY HH24:MI') as ADJUST_DATETIME,
      t.reference_id as RECEIPT_ID,
      t.batch_id as BATCH_ID,
      t.update_qty as UPDATE_QTY,
      t.lock_code as LOCK_CODE,
      s.description as SKU_DESCRIPTION
from  mv_inventory_transaction t
      JOIN timezone tz ON tz.site_id = t.site_id ,
       mv_sku s
where   t.sku_id= s.sku_id
and     t.client_id=s.client_id
and   ( :client is null or :client = t.client_id)
and    ( :site is null or t.site_id  in (:site))
and    ( :owner is null or t.owner_id in (:owner))
and    t.code= 'Adjustment'
and   (t.dstamp+tz.diff/24) between  to_date(:dateFrom, 'DD/mm/yyyy') and to_date(:dateTo,'DD/mm/yyyy')+1
and      (:sku is null or t.sku_id in (:sku))
UNION ALL
(select  /*+ index(s pk_sku) */
     to_char(t.dstamp, 'YYYYmmDDHH24MI') as sort_1,
    t.client_id as CLIENT_ID ,
      t.site_id as SITE_ID,
                      tz.time_zone_name as TIME_ZONE_NAME     ,
      t.owner_id as OWNER_ID,
      t.sku_id as SKU_ID,
      t.reason_id as ADJUST_TYPE,
      to_char(t.dstamp+tz.diff/24, 'DD/mm/YYYY HH24:MI') as ADJUST_DATETIME,
      t.reference_id as RECEIPT_ID,
      t.batch_id as BATCH_ID,
      t.update_qty as UPDATE_QTY,
      t.lock_code as LOCK_CODE,
      s.description as SKU_DESCRIPTION
from  mv_inventory_transaction_arch t
      JOIN timezone tz ON tz.site_id = t.site_id,
       mv_sku s
where   t.sku_id= s.sku_id
and     t.client_id=s.client_id
and   ( :client is null or :client = t.client_id)
and    ( :site is null or t.site_id  in (:site))
and    ( :owner is null or t.owner_id in (:owner))
and    t.code= 'Adjustment'
and   (t.dstamp+tz.diff/24) between  to_date(:dateFrom, 'DD/mm/yyyy') and to_date(:dateTo,'DD/mm/yyyy')+1
and      (:sku is null or t.sku_id in (:sku))
order by sort_1,2,3,4,5
version = Release 10.1.0.5.0
SQL> sho parameter optimizer
NAME                                 TYPE        VALUE
optimizer_dynamic_sampling           integer     2
optimizer_features_enable            string      10.1.0.5
optimizer_index_caching              integer     0
optimizer_index_cost_adj             integer     100
optimizer_mode                       string      ALL_ROWS
sho parameter db_file_multiblock_count_read
sho parameter cursor_sharing
SQL> sho parameter optimizer
NAME                                 TYPE        VALUE
optimizer_dynamic_sampling           integer     2
optimizer_features_enable            string      10.1.0.5
optimizer_index_caching              integer     0
optimizer_index_cost_adj             integer     100
optimizer_mode                       string      ALL_ROWS
SQL>  sho parameter db_file_multi
NAME                                 TYPE        VALUE
db_file_multiblock_read_count        integer     16
SQL> sho parameter cursor_sharing
NAME                                 TYPE        VALUE
cursor_sharing                       string      EXACTExplain plan
| Id  | Operation                              | Name                          | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT                       |                               |    56 | 29736 |   345K  (1)| 01:09:07 |
|   1 |  SORT ORDER BY                         |                               |    56 | 29736 |   345K  (1)| 01:09:07 |
|   2 |   VIEW                                 |                               |    56 | 29736 |   345K  (1)| 01:09:07 |
|   3 |    UNION-ALL                           |                               |       |       |            |          |
|   4 |     NESTED LOOPS                       |                               |     2 |   984 | 29686   (1)| 00:05:57 |
|   5 |      HASH JOIN                         |                               |     1 |   326 | 26870   (1)| 00:05:23 |
|   6 |       TABLE ACCESS FULL                | TIMEZONE                      |     4 |    88 |     3   (0)| 00:00:01 |
|   7 |       VIEW                             | MV_INVENTORY_TRANSACTION      |    25 |  7600 | 26866   (1)| 00:05:23 |
|   8 |        UNION-ALL                       |                               |       |       |            |          |
|   9 |         FILTER                         |                               |       |       |            |          |
|  10 |          MAT_VIEW ACCESS BY INDEX ROWID| MV_INVENTORY_TRANSACTION      |     1 |    67 | 24327   (1)| 00:04:52 |
|  11 |           INDEX RANGE SCAN             | IDX_CODE_CLIENTID_690         | 79681 |       |   518   (1)| 00:00:07 |
|  12 |         FILTER                         |                               |       |       |            |          |
|  13 |          MAT_VIEW ACCESS BY INDEX ROWID| MV_INVENTORY_TRANSACTION      |    24 |  2328 |  2539   (1)| 00:00:31 |
|  14 |           INDEX RANGE SCAN             | IDX_CODE_646                  |  9269 |       |    46   (0)| 00:00:01 |
|  15 |      VIEW                              | MV_SKU                        |    37 |  6142 |  2816   (1)| 00:00:34 |
|  16 |       UNION-ALL                        |                               |       |       |            |          |
|  17 |        MAT_VIEW ACCESS FULL            | MV_SKU                        |   335K|    10M|  2535   (1)| 00:00:31 |
|  18 |        MAT_VIEW ACCESS FULL            | MV_SKU                        | 37839 |  1699K|   280   (1)| 00:00:04 |
|  19 |     NESTED LOOPS                       |                               |    54 | 26568 |   315K  (1)| 01:03:10 |
|  20 |      HASH JOIN                         |                               |     1 |   326 |   313K  (1)| 01:02:37 |
|  21 |       TABLE ACCESS FULL                | TIMEZONE                      |     4 |    88 |     3   (0)| 00:00:01 |
|  22 |       VIEW                             | MV_INVENTORY_TRANSACTION_ARCH |   576 |   171K|   313K  (1)| 01:02:37 |
|  23 |        UNION-ALL                       |                               |       |       |            |          |
|  24 |         FILTER                         |                               |       |       |            |          |
|  25 |          MAT_VIEW ACCESS BY INDEX ROWID| MV_INVENTORY_TRANSACTION_ARCH |     1 |    72 | 19258   (1)| 00:03:52 |
|  26 |           INDEX RANGE SCAN             | QUI_IDX_INVTRANS_ARC1         | 36016 |       |   287   (1)| 00:00:04 |
|  27 |         FILTER                         |                               |       |       |            |          |
|  28 |          MAT_VIEW ACCESS BY INDEX ROWID| MV_INVENTORY_TRANSACTION_ARCH |   575 | 55200 |   293K  (1)| 00:58:45 |
|  29 |           INDEX RANGE SCAN             | QUI_IDX_INVTRANS_ARC1         |   367K|       |  3466   (1)| 00:00:42 |
|  30 |      VIEW                              | MV_SKU                        |    37 |  6142 |  2816   (1)| 00:00:34 |
|  31 |       UNION-ALL                        |                               |       |       |            |          |
|  32 |        MAT_VIEW ACCESS FULL            | MV_SKU                        |   335K|    10M|  2535   (1)| 00:00:31 |
|  33 |        MAT_VIEW ACCESS FULL            | MV_SKU                        | 37839 |  1699K|   280   (1)| 00:00:04 |
------------------------------------------------------------------------------------------------------------------------when put in sql tuning advisor,It recommended with better plan using indexes
| Id  | Operation                              | Name                          | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT                       |                               |    56 | 29736 |   340K  (1)| 01:08:01 |
|   1 |  SORT ORDER BY                         |                               |    56 | 29736 |   340K  (1)| 01:08:01 |
|   2 |   VIEW                                 |                               |    56 | 29736 |   340K  (1)| 01:08:01 |
|   3 |    UNION-ALL                           |                               |       |       |            |          |
|   4 |     NESTED LOOPS                       |                               |     2 |   848 | 26900   (1)| 00:05:23 |
|   5 |      HASH JOIN                         |                               |     1 |   326 | 26898   (1)| 00:05:23 |
|   6 |       TABLE ACCESS FULL                | TIMEZONE                      |     4 |    88 |     3   (0)| 00:00:01 |
|   7 |       VIEW                             | MV_INVENTORY_TRANSACTION      |    25 |  7600 | 26894   (1)| 00:05:23 |
|   8 |        UNION-ALL                       |                               |       |       |            |          |
|   9 |         FILTER                         |                               |       |       |            |          |
|  10 |          MAT_VIEW ACCESS BY INDEX ROWID| MV_INVENTORY_TRANSACTION      |     1 |    67 | 24352   (1)| 00:04:53 |
|  11 |           INDEX RANGE SCAN             | IDX_CODE_CLIENTID_690         | 79681 |       |   518   (1)| 00:00:07 |
|  12 |         FILTER                         |                               |       |       |            |          |
|  13 |          MAT_VIEW ACCESS BY INDEX ROWID| MV_INVENTORY_TRANSACTION      |    24 |  2328 |  2542   (1)| 00:00:31 |
|  14 |           INDEX RANGE SCAN             | IDX_CODE_646                  |  9269 |       |    46   (0)| 00:00:01 |
|  15 |      VIEW                              | MV_SKU                        |    37 |  3626 |     2   (0)| 00:00:01 |
|  16 |       UNION-ALL PARTITION              |                               |       |       |            |          |
|  17 |        MAT_VIEW ACCESS BY INDEX ROWID  | MV_SKU                        |     1 |    34 |     3   (0)| 00:00:01 |
|  18 |         INDEX UNIQUE SCAN              | PK_SKU                        |     1 |       |     2   (0)| 00:00:01 |
|  19 |        MAT_VIEW ACCESS BY INDEX ROWID  | MV_SKU                        |     1 |    46 |     2   (0)| 00:00:01 |
|  20 |         INDEX UNIQUE SCAN              | PK_SKU                        |     1 |       |     1   (0)| 00:00:01 |
|  21 |     NESTED LOOPS                       |                               |    54 | 22896 |   313K  (1)| 01:02:38 |
|  22 |      HASH JOIN                         |                               |     1 |   326 |   313K  (1)| 01:02:38 |
|  23 |       TABLE ACCESS FULL                | TIMEZONE                      |     4 |    88 |     3   (0)| 00:00:01 |
|  24 |       VIEW                             | MV_INVENTORY_TRANSACTION_ARCH |   576 |   171K|   313K  (1)| 01:02:38 |
|  25 |        UNION-ALL                       |                               |       |       |            |          |
|  26 |         FILTER                         |                               |       |       |            |          |
|  27 |          MAT_VIEW ACCESS BY INDEX ROWID| MV_INVENTORY_TRANSACTION_ARCH |     1 |    72 | 19269   (1)| 00:03:52 |
|  28 |           INDEX RANGE SCAN             | QUI_IDX_INVTRANS_ARC1         | 36016 |       |   287   (1)| 00:00:04 |
|  29 |         FILTER                         |                               |       |       |            |          |
|  30 |          MAT_VIEW ACCESS BY INDEX ROWID| MV_INVENTORY_TRANSACTION_ARCH |   575 | 55200 |   293K  (1)| 00:58:47 |
|  31 |           INDEX RANGE SCAN             | QUI_IDX_INVTRANS_ARC1         |   367K|       |  3466   (1)| 00:00:42 |
|  32 |      VIEW                              | MV_SKU                        |    37 |  3626 |     2   (0)| 00:00:01 |
|  33 |       UNION-ALL PARTITION              |                               |       |       |            |          |
|  34 |        MAT_VIEW ACCESS BY INDEX ROWID  | MV_SKU                        |     1 |    34 |     3   (0)| 00:00:01 |
|  35 |         INDEX UNIQUE SCAN              | PK_SKU                        |     1 |       |     2   (0)| 00:00:01 |
|  36 |        MAT_VIEW ACCESS BY INDEX ROWID  | MV_SKU                        |     1 |    46 |     2   (0)| 00:00:01 |
|  37 |         INDEX UNIQUE SCAN              | PK_SKU                        |     1 |       |     1   (0)| 00:00:01 |
------------------------------------------------------------------------------------------------------------------------So ,after checking the recommended plan I tried to execute the query with the hints,even then it is picking up the indexes in the explain plan.So please kindly help in solving the issue
The pk_sku is the index created on client_id and sku_id columns
Thanks
GV

Answer 1

riedelme wrote:
My experience is differernt - hints will be followed if the optimizer determines they will be beneficial and not if they will not, including my current project on 11gR2. The example below (unfortunately only 11gR1) disproves your theory, showing the index hint is followed and that the cost increases by a factor of five.
The most common cases of the optimizer apparently ignoring a hint are due to operator error, the hint is not well formed, or cannot be followed. There are a couple of documented cases where a hint will be ignored - first_rows used in CTAS is one.
Jonathan Lewis writes a lot about it on his blog showing that the optimizer always acts on a well formed hint if it is at all possible.
SQL> create table t (n number not null, c varchar2(1000));
Table created.
SQL> insert into t select 1, rpad('x',1000,'x')
  2  from dual connect by level <= 50000;
50000 rows created.
SQL> create index t_ix on t (n);
Index created.
SQL> exec dbms_stats.gather_table_stats(user, 't', cascade => true)
PL/SQL procedure successfully completed.
SQL> explain plan for
  2  select max(c) from t where n =1;
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 2966233522
| Id  | Operation          | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT   |      |     1 |  1004 |  1574   (1)| 00:00:19 |
|   1 |  SORT AGGREGATE    |      |     1 |  1004 |            |          |
|*  2 |   TABLE ACCESS FULL| T    | 50000 |    47M|  1574   (1)| 00:00:19 |
Predicate Information (identified by operation id):
PLAN_TABLE_OUTPUT
   2 - filter("N"=1)
14 rows selected.
SQL> explain plan for
  2  select /*+ index (t t_ix) */  max(c) from t where n = 1;
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 3231292748
| Id  | Operation                    | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT             |      |     1 |  1004 |  7244   (1)| 00:01:27 |
|   1 |  SORT AGGREGATE              |      |     1 |  1004 |            |          |
|   2 |   TABLE ACCESS BY INDEX ROWID| T    | 50000 |    47M|  7244   (1)| 00:01:27 |
|*  3 |    INDEX RANGE SCAN          | T_IX | 50000 |       |    98   (0)| 00:00:02 |
PLAN_TABLE_OUTPUT
Predicate Information (identified by operation id):
   3 - access("N"=1)
15 rows selected.