mysql查询优化

Question

我的任务是帮助加快此查询，我认为这些表上的某些索引设置不正确。我也相信它们不会全部用于 b/c 一个函数应用于我有索引的 col。谁能看到我如何优化这些表或查询？ requests 表将是 3 个表中最大的一个，将有超过 20 万条记录。 devices 目前大约有 500 条记录，clients 也将更小。

查询:

explain extended SELECT MAX(Request.datetime) AS datetime, Device.id,
       Device.client_id, Device.mac_address, Device.type, Device.manufacturer,
       Device.model_number, Client.id, Client.email_address,
       Request.device_id, Request.datetime, Request.ip_address
  FROM livefi.devices AS Device
  LEFT JOIN livefi.clients AS Client
    ON (Client.id         = Device.client_id)
 INNER JOIN livefi.requests AS Request
    ON (Request.device_id = Device.id)
 GROUP BY Request.device_id, Request.client_id

+----+-------------+---------+--------+---------------------------------------------------------+---------------+---------+-------------------------+------+----------+---------------------------------+
| id | select_type | table   | type   | possible_keys                                           | key           | key_len | ref                     | rows | filtered | Extra                           |
+----+-------------+---------+--------+---------------------------------------------------------+---------------+---------+-------------------------+------+----------+---------------------------------+
|  1 | SIMPLE      | Device  | ALL    | PRIMARY                                                 | NULL          | NULL    | NULL                    |  617 |   100.00 | Using temporary; Using filesort |
|  1 | SIMPLE      | Client  | eq_ref | PRIMARY                                                 | PRIMARY       | 4       | livefi.Device.client_id |    1 |   100.00 |                                 |
|  1 | SIMPLE      | Request | ref    | idx_device_id,inx_requests_deviceId_datetime_ip_address | idx_device_id | 5       | livefi.Device.id        |  144 |   100.00 | Using where                     |
+----+-------------+---------+--------+---------------------------------------------------------+---------------+---------+-------------------------+------+----------+---------------------------------+
3 rows in set, 1 warning (0.04 sec)

表格:

CREATE TABLE `clients` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `email_address` varchar(100) DEFAULT NULL,
  `mac_address` varchar(17) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `email_address` (`email_address`),
  KEY `idx_mac_address` (`mac_address`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8


CREATE TABLE `devices` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `client_id` int(10) unsigned DEFAULT NULL,
  `mac_address` varchar(17) DEFAULT NULL,
  `type` varchar(25) DEFAULT NULL,
  `manufacturer` varchar(100) DEFAULT NULL,
  `model_number` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `mac_address` (`mac_address`),
  KEY `idx_mac_address` (`mac_address`),
  KEY `fk_devices_clients1` (`client_id`),
  CONSTRAINT `fk_devices_clients1` FOREIGN KEY (`client_id`) REFERENCES `clients` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=492 DEFAULT CHARSET=utf8


CREATE TABLE `requests` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `client_id` int(10) unsigned DEFAULT NULL,
  `device_id` int(10) unsigned DEFAULT NULL,
  `domain_id` int(10) unsigned DEFAULT NULL,
  `ip_address` varchar(15) DEFAULT NULL,
  `datetime` datetime DEFAULT NULL,
  `gmt_offset` time DEFAULT NULL,
  `request_method` varchar(15) DEFAULT NULL,
  `url` text,
  `http_protocol` varchar(20) DEFAULT NULL,
  `http_status_code` varchar(20) DEFAULT NULL,
  `request_size` int(10) unsigned DEFAULT '0',
  `referer` text,
  `user_agent` text,
  `squid_cache_response` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `idx_client_id` (`client_id`),
  KEY `idx_datetime` (`datetime`),
  KEY `idx_device_id` (`device_id`),
  KEY `idx_domain_id` (`domain_id`),
  KEY `idx_id` (`id`),
  KEY `idx_request_size` (`request_size`),
  KEY `inx_requests_deviceId_datetime_ip_address` (`device_id`,`datetime`,`ip_address`),
  CONSTRAINT `fk_requests_clients` FOREIGN KEY (`client_id`) REFERENCES `clients` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `fk_requests_devices1` FOREIGN KEY (`device_id`) REFERENCES `devices` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `fk_requests_domains1` FOREIGN KEY (`domain_id`) REFERENCES `domains` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=200523 DEFAULT CHARSET=utf8

Answer 1

我建议:

ALTER TABLE requests ADD INDEX (device_id, client_id, datetime);

此外，请注意，您不应在 SELECT 子句中包含 Request.datetime 或 Request.ip_address，因为它们不属于GROUP BY 子句。这是因为 requests 中的几行可能具有相同的 device_id 和 client_id，并且为 datetime 选择了哪个值或 ip_address 有点随机。