How do the costs of I/O operations differ between index scans and table scans

Index Scan

1. Cost of I/O Operations: Index scans are generally more efficient in terms of I/O operations. They only need to read the index, which is typically smaller than the entire table, resulting in fewer disk accesses.

2. I/O Cost: The I/O cost for an index scan is typically lower because the index is more compact and can be read more quickly.

3. CPU Cost: The CPU cost for an index scan is typically lower because the index is more organized and can be searched more efficiently.

4. Total Operator Cost: The total operator cost for an index scan is typically lower because it includes the I/O and CPU costs.

Table Scan

1. Cost of I/O Operations: Table scans are generally less efficient in terms of I/O operations. They need to read the entire table, which can result in more disk accesses.

2. I/O Cost: The I/O cost for a table scan is typically higher because the table is larger and requires more disk accesses.

3. CPU Cost: The CPU cost for a table scan is typically higher because the table is larger and requires more processing.

4. Total Operator Cost: The total operator cost for a table scan is typically higher because it includes the I/O and CPU costs.

Conclusion

In summary, index scans are generally more efficient in terms of I/O operations and CPU usage compared to table scans. However, the choice between the two depends on the specific requirements and constraints of the query and the database.