Optimizer not using index even after giving the hint

Question

Hi All,
I am wondering why Optimixzer is not using the index in the below query
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
SQL> select column_expression
  2  from ALL_IND_EXPRESSIONS
  3  where table_name like 'GTXN_DTL_V1'
  4  and index_name = 'IDX_TXN11_V1';
COLUMN_EXPRESSION
TO_DATE("BOOKING_DATE",'YYYYMMDD')
SQL> select num_rows from all_tables
  2  where table_name like 'GTXN_DTL_V1';
  NUM_ROWS
  29020867
SQL>  explain plan for select * from gtxn_dtl_v1 where to_date(booking_date,'yyyymmdd') = to_date('030109','DDMMRR');
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 3140624094
| Id  | Operation         | Name        | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |             | 55489 |    15M|   215K  (4)| 00:43:08 |
|*  1 |  TABLE ACCESS FULL| GTXN_DTL_V1 | 55489 |    15M|   215K  (4)| 00:43:08 |
Predicate Information (identified by operation id):
   1 - filter(TO_DATE("BOOKING_DATE",'yyyymmdd')=TO_DATE('030109','DDMMRR
14 rows selected.
--Giving Hint..
SQL> explain plan for select /*+ index(gtxn_dtl_v1 IDX_TXN11_V1) */ *
  2  from gtxn_dtl_v1
  3  where to_date(booking_date,'yyyymmdd') = to_date('030109','DDMMRR')
  4  /
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 3140624094
| Id  | Operation         | Name        | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |             | 55489 |    15M|   215K  (4)| 00:43:08 |
|*  1 |  TABLE ACCESS FULL| GTXN_DTL_V1 | 55489 |    15M|   215K  (4)| 00:43:08 |
Predicate Information (identified by operation id):
   1 - filter(TO_DATE("BOOKING_DATE",'yyyymmdd')=TO_DATE('030109','DDMMRR
14 rows selected.Please suggest.
Thanks in advance,
Jeneesh

Answer 1

porzer wrote:
Hi!
Why are you using the to_date ont the booking_date column? Is it a varchar2 column, what type is it.
Because if it's a varchar2 column you could simply use
select * from gtxn_dtl_v1 where booking_date = '20090103';
So you wouldn't even need a function based index.
On the other hand if it's a date you shouldn't do a to_date as well.
Best regards,
PPThat is not the original qury used in production. I am investigating on the prformance of the below query.
select  txn.account_number,to_number(txn.amount_lcy) txn_amt,to_date(booking_date,'yyyymmdd') TXN_DATE,
      sal.latest_sal,sal.sal_date,customer_name,employer_name,
       decode(COMMUNICATION_TYPE_1,'MOBILE',COMMUNICATION_NO_1,decode(COMMUNICATION_TYPE_2,'MOBILE',COMMUNICATION_NO_2)) mob,
       txn.CURRENCY, CHEQUE_NUMBER,trans_dets,trans_reference,target,teller_id,acc.category,acc.inactive_marker,acc.posting_restrict,cus.sector,cus.industry
from coreadmin.Gtxn_dtl_v1 txn,
               (select account_number,round(to_number(nvl(amount_lcy,0)),2) latest_sal,TXN_DATE sal_date,rr
                from
                  (select to_date(booking_date,'yyyymmdd') TXN_DATE,batch_id,account_number,amount_lcy
                         ,row_number() over (partition by account_number order by to_date(booking_date,'yyyymmdd') desc NULLS LAST,batch_id desc nulls last) rr,
                         CURRENCY, CHEQUE_NUMBER,trans_dets,trans_reference
                    from coreadmin.Gtxn_dtl_v1
                    where transaction_code = '204'
                and to_number(amount_lcy) > 0)
                    where rr = 1
                 ) sal,customers_live cus,accounts_live acc
where to_date(booking_date,'yyyymmdd') between to_date('030109','DDMMRR') and to_date('030209','DDMMRR')
and txn.account_number = sal.account_number
and txn.CUSTOMER_ID = cus.CUSTOMER_number(+)
and acc.id = sal.account_number
and target in ('30','31','32')Edited by: jeneesh on Mar 25, 2009 12:38 PM
Corrected the query.
The column is of VARCHAR2 type. This is because, the table is loaded, through sqlldr, every day from flat files generated form GLOBUS banking system. Column is kept as VARCHAR2 to minimize the loading issues.