問題文
A developer asks how the numbers held in the data dictionary about a table can possibly change which join method the optimizer picks. What is the chain of reasoning?
選択肢
- The statistics hold the plan that was used the last time and the optimizer reuses that plan unless one of the objects in it has been altered since that time.
- The statistics of the columns feed the estimate of the rows that each step returns and the cost of each candidate plan is computed from those counts.
- The statistics fix an upper bound on the rows a step may return and the optimizer rejects any plan whose steps could exceed that bound.
- The statistics record which indexes were used most often and the optimizer prefers the index that appears most frequently in that recorded history of use.