I just wrote an article about “Troubleshooting ‘Waiting for table metadata lock’ Errors for both MyISAM and InnoDB Tables” and then ran into a new, different metadata locking issue right after I posted it, and so I thought I’d share that too, just in case anyone ever encounters a similar situation.

In this case, mysqld kept crashing on restart, reporting “out of memory” errors:

/opt/app/mysql/product/mysql/bin//mysqld: Out of memory (Needed 840 bytes)
stack_bottom = 7fb4ebaeae58 thread_stack 0x40000
mysqld: /mysql/mysys/my_new.cc:52: int __cxa_pure_virtual():
  Assertion `! "Aborted: pure virtual method called."' failed.
mysqld: /mysql/mysys/my_new.cc:52: int __cxa_pure_virtual():
  Assertion `! "Aborted: pure virtual method called."' failed.
Fatal signal 6 while backtracing

There is a …

Ever see an error like this in your console or error log, respectively, and wonder where it originated from?

Console (5.5.30):

ERROR 1017 (HY000): Can't find file:
'.\test\select@0020@002a@0020from@0020t1.frm' (errno: 22)

Error Log (5.5.30):

130307 23:22:04 [ERROR] C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqld: 
Can't find file: '.\test\select@0020@002a@0020from@0020t1.frm' (errno: 22)

(Fwiw, they are harmless, unless it is indicative of some sql injection – but you may want to sanitize your data better, unless it’s just a one-time user error. Also, if you’re seeing it from the command line, then you’ll likely realize what you did immediately, and thus no need to ‘figure out’ what happened. However, when you *only* see this entry in the error log, and you want to know how that happened after the fact, then this is more relevant.)

At any rate, after searching the code, one can see …

I was searching around and was pleasantly surprised when I ran across this new MySQL Troubleshooting book by Sveta Smirnova:

“MySQL Troubleshooting – What To Do When Queries Don’t Work”

http://shop.oreilly.com/product/0636920021964.do

Having worked with Sveta in Support for years, I’m certain this book is chock-full of great troubleshooting techniques and advices (and you can get a good idea from the “Table of Contents” listed on the above page).

I’m always happy to see new MySQL-related books.

Congratulations, Sveta!

MySQL databases are great work horses of the internet.  They back tons of modern websites, from blogs and checkout carts, to huge sites like Facebook.  But these technologies don't run themselves.  When you're faced with a system that is slowing down, you'll need the right tools to diagnose and troubleshoot the problem.  MySQL has a huge community following and that means scores of great tools for your toolbox. Here are 7 ways to troubleshoot MySQL.

1. Use innotop

Innotop is a great tool for MySQL which despite the name monitors MySQL generally as well as InnoDB usage.  It's fairly easy to install, just download the perl script. Be sure to include a [client] section to your local users .my.cnf file (you have one don't you?).  Inside that section, place one line with "user=xyz" and one line with "password=abc".

If you're concerned that installing something new is too …