select * from information_schema.optimizer_trace;

set @@session.optimizer_trace=‘enabled=on,one_line=on‘;

select user,host from mysql.user;+------------+------------+| user       | host       |+------------+------------+| admin      | %          || zabbix     | %          || backupuser | 127.0.0.1  || root       | 127.0.0.1  || zabbix     | 127.0.0.1  || root       | ::1        ||            | localhost  || backupuser | localhost  || root       | localhost  || zabbix     | localhost  ||            | workstudio || root       | workstudio |+------------+------------+

select * from information_schema.optimizer_trace \G*************************** 1. row ***************************                            QUERY: select user,host from mysql.user                            TRACE: {"steps": [{"join_preparation": {"select#": 1,"steps": [{"expanded_query": "/* select#1 */ select `mysql`.`user`.`User` AS `user`,`mysql`.`user`.`Host` AS `host` from `mysql`.`user`"}]}},{"join_optimization": {"select#": 1,"steps": [{"table_dependencies": [{"table": "`mysql`.`user`","row_may_be_null": false,"map_bit": 0,"depends_on_map_bits": []}]},{"rows_estimation": [{"table": "`mysql`.`user`","table_scan": {"rows": 12,"cost": 2}}]},{"considered_execution_plans": [{"plan_prefix": [],"table": "`mysql`.`user`","best_access_path": {"considered_access_paths": [{"access_type": "scan","rows": 12,"cost": 4.6813,"chosen": true}]},"cost_for_plan": 4.6813,"rows_for_plan": 12,"chosen": true}]},{"attaching_conditions_to_tables": {"original_condition": null,"attached_conditions_computation": [],"attached_conditions_summary": [{"table": "`mysql`.`user`","attached": null}]}},{"refine_plan": [{"table": "`mysql`.`user`","access_type": "index_scan"}]}]}},{"join_execution": {"select#": 1,"steps": []}}]}MISSING_BYTES_BEYOND_MAX_MEM_SIZE: 0          INSUFFICIENT_PRIVILEGES: 01 row in set (0.00 sec)