mysql性能在增加数据存储后会下降。需要系统诊断程序的提示

We have an established web application, which is supported by a mysql database. We add data incrementally to various tables on a monthly basis. After recent updates, the database performance has degraded significantly and we had to back out the updates. So far I have identified the queries involved in the web service logic - there are no updates, just reads. I've established that all the queries are using efficient table indexes.We have an established web application, which i