cursor: 57 bills still in the shop
one query per bill: owed Rp 1.529.000, 2954 queries, 18 ms
one query, grouped: owed Rp 1.529.000, 1 query, 3 ms
after close(): 57 rows still in memory, per outlet {'O01': 32, 'O02': 15, 'O03': 10}
