8.9 Controlling the Query Optimizer

8.9.1 Controlling Query Plan Evaluation

8.9.2 Switchable Optimizations

8.9.3 Optimizer Hints

8.9.4 Index Hints

8.9.5 The Optimizer Cost Model

8.9.6 Optimizer Statistics

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 the column_statistics data dictionary table (see Section 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 querying INFORMATION_SCHEMA.COLUMN_STATISTICS, which is implemented as a view on the data dictionary table. You can also perform histogram management using the ANALYZE TABLE statement.