Determinations of rows scanned from disk for a table scan

For table scans, the optimizer does not need to estimate the number of rows that will be scanned from disk during the scan; the number of rows that will be scanned from disk will be equal to the number of rows in the table.

• How the optimizer determines the number of rows in a table
  The optimizer uses a stored row count to determine the number of rows in a table. The stored row count is maintained automatically by the system.