在MySQL 5.7版本以后,mysql库下面新增了两张cost表,主要用途是方便用于来调整MySQL优化器对于不同对象的cost计算方式,例如临时表、扫描行、排序等等。root@mysqldb 21:54: [mysql]> show tables like '%cost%';+--------------------------+| Tables_in_mysql (%cost%) |+--------------------------+| engine_cost || server_cost |+--------------------------+2 rows in set (0.00 sec)Server层一些操作的成本估算项的值特定引擎的一些操作的成本估算项的值engine_costroot@mysqldb 21:54: [mysql]> select * from engine_cost -> ;+-------------+-------------+------------------------+------------+---------------------+---------+| engine_name | device_type | cost_name | cost_value | last_update | comment |+-------------+-------------+------------------------+-----
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