MySQL provides optimizer control through system variables that affect how query plans are evaluated, switchable optimizations, optimizer and index hints, and the optimizer cost model.

The server maintains histogram statistics about column values in thecolumn_statisticsdata dictionary table (seeSection 8.9.6, “Optimizer Statistics”). Like other data dictionary tables, this table is not directly accessible by users. Instead, you can obtain histogram information by queryingINFORMATION_SCHEMA.COLUMN_STATISTICS,它被实现为一个dicti视图的数据onary table. You can also perform histogram management using theANALYZE TABLEstatement.