【发布时间】：2013-10-01 10:26:22
【问题描述】：
这是我第一次尝试在 StackOverflow 上寻求帮助 :)
我有下表：
CREATE TABLE `tinfinite_visits` (
`visit_id` int(255) NOT NULL AUTO_INCREMENT,
`identity_id` int(255) NOT NULL,
`ip` varchar(39) NOT NULL,
`loggedin` enum('0','1') NOT NULL DEFAULT '0',
`url` longtext NOT NULL,
`realurl` longtext NOT NULL,
`referrer` longtext NOT NULL,
`method` enum('GET','POST','HEAD','OPTIONS','PUT','DELETE','TRACE','CONNECT','PATCH') NOT NULL,
`client` longtext NOT NULL,
`referring` longtext NOT NULL,
`timestart` datetime NOT NULL,
`timeend` datetime NOT NULL,
PRIMARY KEY (`visit_id`),
KEY `timestart` (`timestart`),
KEY `identity_id` (`identity_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
在某些时候，我需要从该表中获取一些数据来生成折线图。我目前使用 5 个不同的查询，针对 5 个不同的时间间隔（总计、年、月、周、日）进行此操作。
该表目前有大约 200.000 行，但会变得更大（甚至数千万条记录）。
虽然我的查询非常适合此目的，但我正在努力寻找一种更好的性能方式。
因此，我非常感谢任何关于如何提高查询性能的提示/建议，如果可能的话，最好甚至将所有 5 个查询合并为 1 个。
我目前使用的查询、它们的解释以及它们的执行时间（大约 200.000 行）如下：
日查询：
SELECT COUNT(DISTINCT(`identity_id`)) AS visits, DATE_FORMAT(CONVERT_TZ(timestart, '-5:00', '+3:00'), '%l%p') AS unit
FROM tinfinite_visits
WHERE `timestart` >= DATE_SUB(NOW(), INTERVAL 24 HOUR)
GROUP BY unit
ORDER BY `timestart` ASC
解释：
+----+-------------+----------------------+-------+---------------+-----------+---------+-----+-------+------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------------------+-------+---------------+-----------+---------+-----+-------+------------------------------+
| 1 | SIMPLE | tinfinite_visits | range | timestart | timestart | 8 | | 11113 | Using where; Using temporary |
+----+-------------+----------------------+-------+---------------+-----------+---------+-----+-------+------------------------------+
时间：0.011280059814453
周查询：
SELECT COUNT(DISTINCT(`identity_id`)) AS visits, DATE_FORMAT(CONVERT_TZ(timestart, '-5:00', '+3:00'), '%a') AS unit
FROM tinfinite_visits
WHERE `timestart` >= DATE_SUB(NOW(), INTERVAL 7 DAY)
GROUP BY unit
ORDER BY `timestart` ASC
解释：
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
| 1 | SIMPLE | tinfinite_visits | ALL | timestart | | | | 205897 | Using where; Using temporary; Using filesort |
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
时间：0.13543295860291
月份查询：
SELECT COUNT(DISTINCT(`identity_id`)) AS visits, DATE_FORMAT(CONVERT_TZ(timestart, '-5:00', '+3:00'), '%d') AS unit
FROM tinfinite_visits
WHERE `timestart` >= DATE_SUB(NOW(), INTERVAL 28 DAY)
GROUP BY unit
ORDER BY `timestart` ASC
解释：
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
| 1 | SIMPLE | tinfinite_visits | ALL | timestart | | | | 205897 | Using where; Using temporary; Using filesort |
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
时间：0.21460795402527
年份查询：
SELECT COUNT(DISTINCT(`identity_id`)) AS visits, DATE_FORMAT(`timestart`, '%b') AS unit
FROM tinfinite_visits
WHERE `timestart` >= DATE_SUB(NOW(), INTERVAL 1 YEAR)
GROUP BY unit
ORDER BY `timestart` ASC
解释：
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
| 1 | SIMPLE | tinfinite_visits | ALL | timestart | | | | 205897 | Using where; Using temporary; Using filesort |
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
时间：0.50977802276611
整体查询：
SELECT COUNT(DISTINCT(`identity_id`)) AS visits, DATE_FORMAT(`timestart`, '%b') AS unit
FROM tinfinite_visits
WHERE `timestart` >= DATE_SUB(NOW(), INTERVAL 100 YEAR)
GROUP BY unit
ORDER BY `timestart` ASC
解释：
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
| 1 | SIMPLE | tinfinite_visits | ALL | timestart | | | | 205897 | Using where; Using temporary; Using filesort |
+----+-------------+------------------+------+---------------+-----+---------+-----+--------+----------------------------------------------+
时间：0.52196192741394
非常非常感谢！
【问题讨论】：
-
过早的优化总会带来麻烦。你认为会有多少记录？现在有什么显示
EXPLAIN？ -
@AlmaDoMundo 请查看更新后的问题。谢谢。
-
解释会随着时间而改变。现在它看起来是最佳的。它使用 where 进行过滤，然后存储分组值，然后对这些值进行排序。