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On my server I have 6 MySQL databases. They all power Wordpress websites. For some reason, 2 of these databases are not accessible. To my knowledge they use INNODB, but I can't confirm it as even doing a:

mysql> use INFORMATION_SCHEMA;
mysql> SELECT * FROM TABLES;

hangs on me. The working databases seem fine (at least the websites are online). When I tried to access the bad database websites, it will just keep spinning.

If I do a:

mysql> use rbb;
mysql> SELECT * FROM wp_posts;

It will just hang.

My server is running CentOS 6.2 and up to now i've had no issues.

Any pointers would be much appreciated. I have no idea what to do next.

Even opening a Sequel Pro to the server hangs the application.

If I try a query and then check the process list in another connection, it shows:

+----+------+-----------+-----+---------+------+----------------+------------------------+
| Id | User | Host      | db  | Command | Time | State          | Info                   |
+----+------+-----------+-----+---------+------+----------------+------------------------+
| 10 | root | localhost | rbb | Query   | 45   | Opening tables | SELECT * FROM wp_users |
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1  
Check your MySQL logfile for any error messages. –  etagenklo Dec 7 '13 at 22:04
    
Tried rebooting/restarting MySQL? Indeed also check MySQL error logs, usually somewhere in /var/log or /var/lib/mysql file is usually called [hostname].err. If you use Linux you can try to find it run: find / -name *.err –  edwardmp Dec 7 '13 at 23:46

2 Answers 2

According to the mysql documentation, the 'opening tables' state shouldn't be seen unless there are locks getting in the way, or when your table_open_cache is too small.

Check mysql's errorlog to find out what happened, check the show engine innodb status output for innodb info.

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And a relevant older thread ... stackoverflow.com/questions/10904044/… –  Nikolaidis Fotis Dec 9 '13 at 9:36

Maybe a mutex / lock went wild ?

Probably a restart will fix. Otherwise you can check if there are any locks and release them by hand.

Try with SHOW FULL PROCESSLIST;

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Tried a restart and it didn't work. Also, the FULL PROCESSLIST only shows 1 query and that is the PROCESSLIST query. –  Thomas Lomas Dec 8 '13 at 12:44

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