Cost Model for Our Analysis
We ignore CPU costs, for simplicity:
- B: The number of data pages
- R: Number of records per page
- D: (Average) time to read or write disk page
- Measuring number of page I/O’s ignores gains of pre-fetching blocks of pages; thus, even I/O cost is only approximated.
- Average-case analysis; based on several simplistic assumptions.
- Good enough to show the overall trends!