然而需要注意的是，先进的优化器在生成一个特定的访问计划时，必然有其原因，所以在应用指南之前，务必理解是什么原因导致查询的性能低下。

However, note that the state-of-the-art optimizer has a reason to generate a particular access plan, so it is important to ensure that we understand the inefficiency before we apply the guidelines.

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