•Hash-index on name of Person (as inner):
–Scan Purchase:
1000 page I/Os, 100*1000 tuples.
–For each Person tuple:
1.2 I/Os to get data entry in index, plus 1 I/O to get (the exactly one) matching Person tuple. Total:
220,000 I/Os. (36 minutes)
•Hash-index on buyer of Purchase (as inner):
–Scan Person: 500
page I/Os, 80*500 tuples.
–For each Person tuple:
1.2 I/Os to find index page with data entries, plus cost of retrieving matching Purchase
tuples. Assuming uniform distribution, 2.5 purchases per buyer
(100,000 / 40,000). Cost of retrieving them is 1 or 2.5 I/Os depending on clustering.