1. Operations to Consider
Scan: fetch all records in a certain relation.
Search with equality selection: find all the tuples with age=5
Search range selection: find all tuples with age between 5 and 50
Insert: put a new record into the file.
Delete: a record from the file.

2. Costs to Measure B data pages, R records per page.
Average time to read or write a disk page: D (typically 15msec)
Average time to process a record: C (typically 1 to 10 microsec)
Time to apply hash function: H (typically 1 to 10 microsec)
So, we count mostly I/O costs.

3. Indexes
Auxiliary structure that speeds up operations that are not supported
by the basic file organization.
Formally: a set of data entries with an efficient way of locating
all the entries with search key k.
Questions: how are the data entries organized to support the
efficient access?
What is a data entry exactly?
Options for data entry: 1. An actual data record (whose value is k)
2. A pair (k, rid) - pointer to the real record.
3. A pair (k, list-of-rid)

4. Properties of Indexes
- clustered vs. unclustered (how many clustered indexes can
we have on a file?)
- Dense vs. sparse indexes
- Primary and secondary indexes (is the key entry a superkey?)

5. Picture slides missing here...