Subquery Factoring -Performance Issue

Question

Hi experts,
Oracle 10G
select
a.colums,
b.columns
from
( select
Colums
from
F ,
(select
columns
from
bigtable
where
<condition with recdate and modified date with timezone convertions Given as in end of this qury)
) a,
( select
Colums
from
tables,
(select
columns
from
bigtable
where
<condition with recdate and modified date with timezone convertions Given as in end of this qury)
) b
(TO_DATE(TO_CHAR(FROM_TZ(CAST(CF.RECDT as timestamp),'GMT') at time zone 'America/Chicago','YYYY-MM-DD
HH24:MI:SS'),'YYYY-MM-DD HH24:MI:SS')
     BETWEEN TO_DATE('01-JAN-2009 00:00:00','DD-MON-YYYY HH24:MI:SS') AND TO_DATE('08-JAN-2009 00:00:00', 'DD-MON-YYYY
HH24:MI:SS')) OR
(TO_DATE(TO_CHAR(FROM_TZ(CAST(CF.MODIFID_DT as timestamp),'GMT') at time zone 'America/Chicago','YYYY-MM-DD
HH24:MI:SS'),'YYYY-MM-DD HH24:MI:SS')
BETWEEN TO_DATE('01-JAN-2009 00:00:00','DD-MON-YYYY HH24:MI:SS') AND TO_DATE('08-JAN-2009 00:00:00', 'DD-MON-YYYY
HH24:MI:SS'))
Recdt - indexed
Modifieddt - not iddexed
bigtable used many times in select to avoid Subquery factoring used (with select) but it increased cost as per explain plan in sqldevleoper please suggest me to increase performance
Lots of thanks,
Kalinga

Answer 1

now the above query use as
with subfact as
( select
select
columns
from
bigtable
where
<condition with recdate and modified date
select
a.colums,
b.columns
from
( select
Colums
from
F ,
subfact
where condition
) a,
( select
Colums
from
tables,
subfact
where condition
) b
it is cost increased in nested loop in explain plan why? is thre any other detail required.