| Bug #69643 | MySQL Cluster select count(*) very slow on concurrent 200 | ||
|---|---|---|---|
| Submitted: | 2 Jul 2013 2:22 | Modified: | 19 Sep 2013 12:06 |
| Reporter: | sam sha | Email Updates: | |
| Status: | No Feedback | Impact on me: | |
| Category: | MySQL Cluster: Cluster (NDB) storage engine | Severity: | S5 (Performance) |
| Version: | 7.3 | OS: | Linux (centos 6.3) |
| Assigned to: | Assigned Account | CPU Architecture: | Any |
| Tags: | MySQL Cluster concurrent 200 select count(*) | ||
[19 Aug 2013 12:06]
Gustaf Thorslund
Sam,
Could you please provide the output of:
mysql> show create table phpbb_sessions;
mysql> explain SELECT COUNT(session_id) AS sessions
FROM phpbb_sessions
WHERE session_user_id = 1
AND session_time >= 1372239407;
You might also be interested in looking at:
mysql> select min(session_time), max(session_time), avg(session_time), std(session_time);
While running these queries do you run any other queries? Do you get any errors when running any queries? In that case what errors and how do you handle them?
/Gustaf
[20 Sep 2013 1:00]
Bugs System
No feedback was provided for this bug for over a month, so it is being suspended automatically. If you are able to provide the information that was originally requested, please do so and change the status of the bug back to "Open".
Description: Table : phpbb_sessions Field Type Extra P session_id varchar(32) session_user_id mediumint(8) UNSIGNED session_forum_id mediumint(8) UNSIGNED session_last_visit int(11) UNSIGNED session_start int(11) UNSIGNED session_time int(11) UNSIGNED session_ip varchar(40) session_browser varchar(150) session_forwarded_for varchar(255) session_page varchar(255) session_viewonline tinyint(1) UNSIGNED session_autologin tinyint(1) UNSIGNED session_admin tinyint(1) UNSIGNED Index Fields Extra session_user_id session_user_id session_time session_time session_forum_id session_forum_id session_uti session_user_id, session_time, session_id --------------------------------------------------------------------- SQL: SELECT COUNT(session_id) AS sessions FROM phpbb_sessions WHERE session_user_id = 1 AND session_time >= 1372239407; records number is 20000 - 30000. run the sql alone is normal , time use 0.0x s。 but when I use apache bench， cocurrent number more bigger， the sql is more and more slowly。 What is abnormal is time used is over 30s when concurent number is 100 - 200 , but other sql query is very fast . how can i resolve it? thank you! 1 How to repeat: write a php, use web application to call the sql, then use apache bench concurrent call the php。