The support page now asks for the visits of one user on one day. A report asks for all the visits of one day.

1. Create an index named visits_user_day_idx on visits, on user_id and then visited_on.
2. Show the plan of SELECT * FROM visits WHERE user_id = 4242 AND visited_on = '2025-06-17'. Which kind of scan does it use?
3. Think before you run it: can visits_user_day_idx serve SELECT * FROM visits WHERE visited_on = '2025-06-17'? user_id has 10 000 different values. Answer yes or no.
4. Show the plan of that day query to check.
5. Make the day query use an index. Then show its plan again.