MySQL执行缓慢执行选择查询

Question

我有以下查询...

SELECT DISTINCT * FROM 
vPAS_Posts_Users 
WHERE (post_user_id =:id AND post_type != 4) 
AND post_updated >:updated 
GROUP BY post_post_id 
UNION 
SELECT DISTINCT vPAS_Posts_Users.* FROM PAS_Follow 
JOIN vPAS_Posts_Users ON 
( PAS_Follow.folw_followed_user_id = vPAS_Posts_Users.post_user_id ) 
WHERE (( PAS_Follow.folw_follower_user_id =:id AND PAS_Follow.folw_deleted = 0 ) 
OR ( post_type = 4 AND post_passed_on_by = PAS_Follow.folw_follower_user_id 
AND post_user_id !=:id )) 
AND post_updated >:updated 
GROUP BY post_post_id ORDER BY post_posted_date DESC LIMIT :limit

例如:id = 7，:updated = 0.0和:limit=40

我的问题是查询大约需要一分钟才能返回结果。我可以在此查询中做些什么来加快结果？

我正在使用RDS

******** ********* EDIT

我被要求用EXPLAIN运行查询，结果在

之下

******** EDIT ********** 查看定义

CREATE ALGORITHM=UNDEFINED DEFINER=`MySQLUSer`@`%` SQL SECURITY DEFINER VIEW `vPAS_Posts_Users`
AS SELECT
   `PAS_User`.`user_user_id` AS `user_user_id`,
   `PAS_User`.`user_country` AS `user_country`,
   `PAS_User`.`user_city` AS `user_city`,
   `PAS_User`.`user_company` AS `user_company`,
   `PAS_User`.`user_account_type` AS `user_account_type`,
   `PAS_User`.`user_account_premium` AS `user_account_premium`,
   `PAS_User`.`user_sign_up_date` AS `user_sign_up_date`,
   `PAS_User`.`user_first_name` AS `user_first_name`,
   `PAS_User`.`user_last_name` AS `user_last_name`,
   `PAS_User`.`user_avatar_url` AS `user_avatar_url`,
   `PAS_User`.`user_cover_image_url` AS `user_cover_image_url`,
   `PAS_User`.`user_bio` AS `user_bio`,
   `PAS_User`.`user_telephone` AS `user_telephone`,
   `PAS_User`.`user_dob` AS `user_dob`,
   `PAS_User`.`user_sector` AS `user_sector`,
   `PAS_User`.`user_job_type` AS `user_job_type`,
   `PAS_User`.`user_unique` AS `user_unique`,
   `PAS_User`.`user_deleted` AS `user_deleted`,
   `PAS_User`.`user_updated` AS `user_updated`,
   `PAS_Post`.`post_post_id` AS `post_post_id`,
   `PAS_Post`.`post_language_id` AS `post_language_id`,
   `PAS_Post`.`post_type` AS `post_type`,
   `PAS_Post`.`post_promoted` AS `post_promoted`,
   `PAS_Post`.`post_user_id` AS `post_user_id`,
   `PAS_Post`.`post_posted_date` AS `post_posted_date`,
   `PAS_Post`.`post_latitude` AS `post_latitude`,
   `PAS_Post`.`post_longitude` AS `post_longitude`,
   `PAS_Post`.`post_location_name` AS `post_location_name`,
   `PAS_Post`.`post_text` AS `post_text`,
   `PAS_Post`.`post_media_url` AS `post_media_url`,
   `PAS_Post`.`post_image_height` AS `post_image_height`,
   `PAS_Post`.`post_link` AS `post_link`,
   `PAS_Post`.`post_link_title` AS `post_link_title`,
   `PAS_Post`.`post_unique` AS `post_unique`,
   `PAS_Post`.`post_deleted` AS `post_deleted`,
   `PAS_Post`.`post_updated` AS `post_updated`,
   `PAS_Post`.`post_original_post_id` AS `post_original_post_id`,
   `PAS_Post`.`post_original_type` AS `post_original_type`,
   `PAS_Post`.`post_passed_on_by` AS `post_passed_on_by`,
   `PAS_Post`.`post_passed_on_caption` AS `post_passed_on_caption`,
   `PAS_Post`.`post_passed_on_fullname` AS `post_passed_on_fullname`,
   `PAS_Post`.`post_passed_on_avatar_url` AS `post_passed_on_avatar_url`
FROM (`PAS_User` join `PAS_Post` on((`PAS_User`.`user_user_id` = `PAS_Post`.`post_user_id`)));

Answer 1

尝试此查询：

SELECT * 
FROM 
    vPAS_Posts_Users 
WHERE 
    post_user_id =:id 
AND post_type != 4 
AND post_updated > :updated 
UNION 
SELECT u.* 
FROM vPAS_Posts_Users u
        JOIN PAS_Follow f ON f.folw_followed_user_id = u.post_user_id
WHERE 
    u.post_updated > :updated
AND (   (f.folw_follower_user_id = :id AND f.folw_deleted = 0) 
    OR  (u.post_type = 4 AND u.post_passed_on_by = f.folw_follower_user_id AND u.post_user_id != :id)
) 
ORDER BY u.post_posted_date DESC;
LIMIT :limit

---

其他改进

<强>指数： 请确保您在以下列中有索引：

• PAS_User.user_user_id
• PAS_Post.post_user_id
• PAS_Post.post_type
• PAS_Post.post_updated
• PAS_Follow.folw_followed_user_id
• PAS_Follow.folw_deleted
• PAS_Post.post_passed_on_by

完成之后，请再次检查性能（SQL_NO_CACHE）并提取另一个解释计划，以便我们调整查询。

---

EXPLAIN结果

Answer 2

以下是查询和查看的一些建议，首先使用UNION对两个结果集进行操作，这可能会使您的查询工作变慢，而您可以使用UNION ALL

为什么我指的是使用UNION ALL

原因是UNION ALL和UNION都使用临时表来生成结果。执行速度的差异来自事实UNION需要带索引的内部临时表（跳过重复行）虽然UNION ALL将创建没有此类索引的表。这解释了使用UNION ALL时性能略有提升。 UNION本身将删除任何重复的记录，因此不需要使用DISTINCT子句，尝试只有子查询的整个结果集的一个GROUP BY，这也将最小化执行时间而不是分组结果在每个子查询中。

确保您已在列上添加了正确的索引，尤其是WHERE,ORDER BY, GROUP BY中使用的列，数据类型应适合每个列的数据性质，如post_posted_date应该是datetime，带索引的日期。

以下是查询的粗略构思

SELECT q.* FROM (
SELECT * FROM 
vPAS_Posts_Users 
WHERE (post_user_id =:id AND post_type != 4) 
AND post_updated >:updated 

UNION ALL


SELECT vPAS_Posts_Users.* FROM PAS_Follow 
JOIN vPAS_Posts_Users ON 
( PAS_Follow.folw_followed_user_id = vPAS_Posts_Users.post_user_id 
AND vPAS_Posts_Users.post_updated >:updated) 
WHERE (( PAS_Follow.folw_follower_user_id =:id AND PAS_Follow.folw_deleted = 0 ) 
OR ( post_type = 4 AND post_passed_on_by = PAS_Follow.folw_follower_user_id 
AND post_user_id !=:id )) 

) q
GROUP BY q.post_post_id ORDER BY q.post_posted_date DESC LIMIT :limit

参考文献

Difference Between Union vs. Union All – Optimal Performance Comparison

Optimize Mysql Union

MySQL Performance Blog

Answer 3

从你的解释中我可以看到你的大多数表都没有任何键，除了主键，我建议你在你要加入的列上添加一些额外的键，例如：PAS_Follow .folw_followed_user_id和vPAS_Posts_Users.post_user_id，这将带来巨大的性能提升。

再见 Gnagno