When deleting a large amount of data, it is recommended to use Delete from t where xx limit 5000;. It deletes through the loop and uses Affected Rows == 0 as a condition to end the loop, so as not to exceed the limit of transaction size. With the prerequisite of meeting business filtering logic, it is recommended to add a strong filter index column or directly use the primary key to select the range, such as id >= 5000*n+m and id < 5000*(n+1)+m.
If the amount of data that needs to be deleted at a time is very large, this loop method will get slower and slower because each deletion traverses backward. After deleting the previous data, lots of deleted flags remain for a short period (then all will be processed by Garbage Collection) and influence the following Delete statement. If possible, it is recommended to refine the Where condition. See details in TiDB Best Practices.