get array data with range

hi, all

1. can i do something this in postgresql
"SELECT array_data[1..20] FROM mytable WHERE condition"
i want to get certain data with range in my array data.
if i fetch all data, it took take a long time (very long time just for fetch
from database).

i'm trying with maximum array size (for me it's very big)
"INSERT INTO mytable(mytable_id, array_data) VALUES(1, '{1,2,3,.......so on
until 1000000}')"
it's fast when insert or update :-), but very slow when fetch/select :-(

is there a trick to do it?

second question.
2. which are better (from speed and size side)?
i make "one" table with array like this
TABLE mytable
mytable_id | array_data
-------------------------------------
1 | {1,2,...,100000}
2 | {1,2,...,100000}
3 | {1,2,...,100000}
....

or like this one, many table but no array
TABLE mytable_1
was_array_data
----------------
1
2
...
100000

TABLE mytable_2
was_array_data
----------------
1
2
...
100000

TABLE mytable_3
...

Thanks in advance

Best Regards
Johny Jugianto