問題文
An execution plan is displayed with both the estimated number of rows and the actual number of rows for every step. One step shows an estimate of two rows and an actual count of ninety thousand rows. What does that tell the analyst?
選択肢
- The plan was produced without running the statement so the actual column holds the default value that the display uses for such a case.
- The statement was run with a different set of bind values from the ones that were used at optimization so the plan shown belongs to another execution of the statement.
- The optimizer worked from a wrong cardinality at that point so the operations chosen above that step suit the volume that a much smaller result would carry.
- The step was executed in parallel so the actual count includes the rows that every parallel server produced while the estimate covers one of them.