# Candidate indexes: one per line, table(column, column, ...).
# The advisor may build any subset of them.
Bill(arrived)
Bill(Outlet_id)
Bill(status)
Bill(Customer_id)
Bill(Service_id)
Bill(Outlet_id, status)
Bill(status, Outlet_id)
Bill(Outlet_id, arrived)
Bill(Customer_id, arrived)
Bill(arrived, Service_id)
Payment(Bill_id)
Payment(paid_at)
Payment(method)
Payment(method, paid_at)
Payment(paid_at, method)
Customer(phone)
StatusLog(Bill_id)
StatusLog(Bill_id, changed_at)
StatusLog(status)
StatusLog(status, changed_at)
StatusLog(changed_at)
StatusLog(Employee_id)
