mysql 8.0.20优化器成本记录表

mysql> select * from engine_cost;
+-------------+-------------+------------------------+------------+---------------------+---------+---------------+
| engine_name | device_type | cost_name              | cost_value | last_update         | comment | default_value |
+-------------+-------------+------------------------+------------+---------------------+---------+---------------+
| default     |           0 | io_block_read_cost     |       NULL | 2020-12-08 21:53:01 | NULL    |             1 |
| default     |           0 | memory_block_read_cost |       NULL | 2020-12-08 21:53:01 | NULL    |          0.25 |
+-------------+-------------+------------------------+------------+---------------------+---------+---------------+
2 rows in set (0.00 sec)

mysql> show create table engine_costG
*************************** 1. row ***************************
       Table: engine_cost
Create Table: CREATE TABLE `engine_cost` (
  `engine_name` varchar(64) NOT NULL,
  `device_type` int NOT NULL,
  `cost_name` varchar(64) NOT NULL,
  `cost_value` float DEFAULT NULL,
  `last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `comment` varchar(1024) DEFAULT NULL,
  `default_value` float GENERATED ALWAYS AS ((case `cost_name` when _utf8mb3'io_block_read_cost' then 1.0 when _utf8mb3'memory_block_read_cost' then 0.25 else NULL end)) VIRTUAL,
  PRIMARY KEY (`cost_name`,`engine_name`,`device_type`)
) /*!50100 TABLESPACE `mysql` */ ENGINE=InnoDB DEFAULT CHARSET=utf8 STATS_PERSISTENT=0 ROW_FORMAT=DYNAMIC
1 row in set (0.00 sec)

mysql> select * from server_cost;
+------------------------------+------------+---------------------+---------+---------------+
| cost_name                    | cost_value | last_update         | comment | default_value |
+------------------------------+------------+---------------------+---------+---------------+
| disk_temptable_create_cost   |       NULL | 2020-12-08 21:53:01 | NULL    |            20 |
| disk_temptable_row_cost      |       NULL | 2020-12-08 21:53:01 | NULL    |           0.5 |
| key_compare_cost             |       NULL | 2020-12-08 21:53:01 | NULL    |          0.05 |
| memory_temptable_create_cost |       NULL | 2020-12-08 21:53:01 | NULL    |             1 |
| memory_temptable_row_cost    |       NULL | 2020-12-08 21:53:01 | NULL    |           0.1 |
| row_evaluate_cost            |       NULL | 2020-12-08 21:53:01 | NULL    |           0.1 |
+------------------------------+------------+---------------------+---------+---------------+
6 rows in set (0.00 sec)

mysql> show create table server_costG
*************************** 1. row ***************************
       Table: server_cost
Create Table: CREATE TABLE `server_cost` (
  `cost_name` varchar(64) NOT NULL,
  `cost_value` float DEFAULT NULL,
  `last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `comment` varchar(1024) DEFAULT NULL,
  `default_value` float GENERATED ALWAYS AS ((case `cost_name` when _utf8mb3'disk_temptable_create_cost' then 20.0 when _utf8mb3'disk_temptable_row_cost' then 0.5 when _utf8mb3'key_compare_cost' then 0.05 when _utf8mb3'memory_temptable_create_cost' then 1.0 when _utf8mb3'memory_temptable_row_cost' then 0.1 when _utf8mb3'row_evaluate_cost' then 0.1 else NULL end)) VIRTUAL,
  PRIMARY KEY (`cost_name`)
) /*!50100 TABLESPACE `mysql` */ ENGINE=InnoDB DEFAULT CHARSET=utf8 STATS_PERSISTENT=0 ROW_FORMAT=DYNAMIC
1 row in set (0.01 sec)