Optimizer Cost When Combinig Bitmap Indexes
In 11.2.0.2
When i combine 2 bitmap indexes it appears that the cost of combining them is: the cost of cheapest index x 2.
Let me know if my understanding is correct ?
Thanks,
For example:
a.) when using the first index it has a cost of 491
select
account
from t1
where
account = 'N'
cost = 491
b.) when using the second index it has a cost of 1
select
date
from t1
where
Eff_Date = DATE'2011-06-01'
cost = 1
c.) when combining them... the cost is 2 which is: cost of cheapest index (1) x 2
select
count(*)
from t1
where
Date = DATE'2011-06-01'
and account = 'N'