Control Execution Plan

The first two chapters of SQL Tuning introduce how to understand TiDB's execution plan and how TiDB generates an execution plan. This chapter introduces what methods can be used to control the generation of the execution plan when you determine the problems with the execution plan. This chapter mainly includes the following three aspects:

• In Optimizer Hints, you will learn how to use hints to guide TiDB to generate an execution plan.
• But hints change the SQL statement intrusively. In some scenarios, hints cannot be simply inserted. In SQL Plan Management, you will know how TiDB uses another syntax to non-intrusively control the generation of execution plans, and the methods of automatic execution plan evolution in the background to alleviate the execution plan instability caused by reasons such as version upgrades, which degrades cluster performance.
• Finally, you will learn how to use the blocklist in Blocklist of Optimization Rules and Expression Pushdown.