| title | summary |
|---|---|
SQL Logical Optimization |
SQL Logical Optimization chapter explains key logic rewrites in TiDB query plan generation. For example, `IN` sub-query `t.a in (select t1.a from t1 where t1.b=t.b)` does not exist due to TiDB rewrites. Key rewrites include Subquery Related Optimizations, Column Pruning, Decorrelation of Correlated Subquery, Eliminate Max/Min, Predicates Push Down, Partition Pruning, TopN and Limit Operator Push Down, and Join Reorder. |
This chapter explains some key logic rewrites to help you understand how TiDB generates the final query plan. For example, when you execute the select * from t where t.a in (select t1.a from t1 where t1.b=t.b) query in TiDB, you will find that the IN sub-query t.a in (select t1.a from t1 where t1.b=t.b) does not exist because TiDB has made some rewrites here.
This chapter introduces the following key rewrites: