View Pushed Predicate - Index Usage

Hi Team,

We are using 19c database.

We need your guidance in below query. We are doing test to force view pushed predicate, We got it but the index inside the view is not used.

Have index on order_id column in LINE_ITEMS tables, why it is not used. Is it expected? If i want to force the index, how can we achieve that.

SQL>
SQL> CREATE TABLE orders (
order_id NUMBER PRIMARY KEY,
customer_id NUMBER,
order_date DATE
);
2 3 4 5
Table created.

SQL> CREATE TABLE line_items (
item_id NUMBER,
order_id NUMBER, -- Will be joined to orders