我正在开发一个社交网络跟踪应用程序。即使连接正确,也可以正常工作。但是,当我添加order by子句时,总查询执行时间要长100倍。我用来获取不带有order by子句的twitter_users的以下查询。
SELECT DISTINCT `tracked_twitter`.id
FROM tracked_twitter
INNER JOIN `twitter_content` ON `tracked_twitter`.`id` = `twitter_content`.`tracked_twitter_id`
INNER JOIN `tracker_twitter_content` ON `twitter_content`.`id` = `tracker_twitter_content`.`twitter_content_id`
AND `tracker_twitter_content`.`tracker_id` = '88'
LIMIT 20
显示第0-19行(共20行,查询耗时0.0714秒)
但是当我添加order by子句(在索引列上)
SELECT DISTINCT `tracked_twitter`.id
FROM tracked_twitter
INNER JOIN `twitter_content` ON `tracked_twitter`.`id` = `twitter_content`.`tracked_twitter_id`
INNER JOIN `tracker_twitter_content` ON `twitter_content`.`id` = `tracker_twitter_content`.`twitter_content_id`
AND `tracker_twitter_content`.`tracker_id` = '88'
ORDER BY tracked_twitter.followers_count DESC
LIMIT 20
显示第0-19行(共20行,查询耗时13.4636秒)
当我仅在其表中实现order by子句时,不会花费太多时间
SELECT * FROM `tracked_twitter` WHERE 1 order by `followers_count` desc limit 20
显示第0-19行(共20行,查询耗时0.0711秒)[followers_count:68236387-10525612]
表创建查询如下
CREATE TABLE IF NOT EXISTS `tracked_twitter` (
`id` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`handle` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`name` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`location` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`description` text COLLATE utf8_unicode_ci,
`profile_image` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`followers_count` int(11) NOT NULL,
`is_influencer` tinyint(1) NOT NULL DEFAULT '0',
`created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
`updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
`gender` enum('Male','Female','Other') COLLATE utf8_unicode_ci
DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `followers_count` (`followers_count`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
因此,当我在其表上执行查询时,join并不会因工作良好而减慢查询和顺序。那么如何提高性能呢?
更新1
@GordonLinoff方法解决是否只需要父表的结果集。我想知道每人tweets的数量(与tracked_twitter表匹配的twitter_content的数量)。我该如何修改?如果我想在推文内容上使用数学函数,该怎么做?
SELECT `tracked_twitter` . * , COUNT( * ) AS twitterContentCount, retweet_count + favourite_count + reply_count AS engagement
FROM `tracked_twitter`
INNER JOIN `twitter_content` ON `tracked_twitter`.`id` = `twitter_content`.`tracked_twitter_id`
INNER JOIN `tracker_twitter_content` ON `twitter_content`.`id` = `tracker_twitter_content`.`twitter_content_id`
WHERE `is_influencer` != '1'
AND `tracker_twitter_content`.`tracker_id` = '88'
AND `tracked_twitter_id` != '0'
GROUP BY `tracked_twitter`.`id`
ORDER BY twitterContentCount DESC
LIMIT 20
OFFSET 0
尝试摆脱distinct
。那是性能杀手。我不确定为什么您的第一个查询会很快工作;也许MySQL足够聪明,可以对其进行优化。
我会尝试:
SELECT tt.id
FROM tracked_twitter tt
WHERE EXISTS (SELECT 1
FROM twitter_content tc INNER JOIN
tracker_twitter_content ttc
ON tc.id = ttc.twitter_content_id
WHERE ttc.tracker_id = 88 AND
tt.id = tc.tracked_twitter_id
)
ORDER BY tt.followers_count DESC ;
对于此版本,您想对指数:tracked_twitter(followers_count, id)
,twitter_content(tracked_twitter_id, id)
,和tracker_twitter_content(twitter_content_id, tracker_id)
。
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我来说两句