Two pages of the site are slow. The login page finds a member by username. The support page finds every visit of one user in visits.

1. Create an index named members_username_idx on the username column of members.
2. Show the plan of SELECT * FROM members WHERE username = 'monster4242'. Which kind of scan does it use?
3. Create an index named visits_user_id_idx on the user_id column of visits.
4. Show the plan of SELECT * FROM visits WHERE user_id = 4242. What is the first step on the top line of the plan?
5. The support page moved to another system. Remove visits_user_id_idx.