Index slows down query execution

Question

Hello everybody,
I have reordered the join conditions for the query...
select (first_name||' '||middle_name||' '||last_name) name,regn_no,age,gender,
(select loc_name from locations where loc_id=location_code and loc_h_id='L6') district,
person_id from persons p,musers u where reg_center_id=u.center_id and
p.ipop='RG' and u.user_id = '8832' and u.eff_end_dt is null and p.CID = '1' order by p.crt_dt desc
like this...
select (first_name||' '||middle_name||' '||last_name) name,regn_no,age,gender,
(select loc_name from locations where loc_id=location_code and loc_h_id='L6') district,
person_id from musers u, persons p where reg_center_id=u.center_id and u.user_id = '8832'
and p.ipop='RG' and u.eff_end_dt is null and p.CID = '1'
because
select count(*) from persons p, musers u where reg_center_id=u.center_id and
p.ipop='RG' is 13002
and
select count(*) from persons p, musers u where reg_center_id=u.center_id and u.user_id = '8832' is 1007.
In this excercise I have a couple of questions..
1. This did not show any difference in the CPU time.
and,
I have created an index 'idx_ipop_persons' on persons(ipop) "create index idx_ipop_persons on persons(ipop)".
2. The query is taking more time to execute than it was before creating the index.
Please help me...
Thanks,
Aswin.

Answer 1

Please post the execution plan for your query.
And also i need some details:
select count(*) from person where ipop='RG';
How many records fetch?
select distinct ipop from persons; --How many
records fetch?
Regards
RajaBaskar
Execution plan:
Execution Plan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=921 Card=176 Bytes
=11088)
1 0 TABLE ACCESS (BY INDEX ROWID) OF 'LOCATIONS' (TABLE)
(Cost=2 Card=1 Bytes=38)
2 1 INDEX (RANGE SCAN) OF 'IDX_LOCID_LOCHDR_LOCATIONS' (INDE
X) (Cost=1 Card=1)
3 0 TABLE ACCESS (BY INDEX ROWID) OF 'PERSONS' (TABLE) (
Cost=918 Card=176 Bytes=9152)
4 3 NESTED LOOPS (Cost=921 Card=176 Bytes=11088)
5 4 TABLE ACCESS (BY INDEX ROWID) OF 'MUSERS' (TA
BLE) (Cost=3 Card=1 Bytes=11)
6 5 INDEX (RANGE SCAN) OF 'PK_MUSERS' (INDEX (UNIQUE)
) (Cost=2 Card=1)
7 4 INDEX (RANGE SCAN) OF 'IDX2_PERSONS' (INDEX) (Co
st=1 Card=1464)
select count(*) from person where ipop='RG';
count(*)
12135
select distinct ipop from persons;
distinct ipop
RG
OP
IP
RF
CR