The MySQL optimizer makes the decision of what execution plan to use based on the information provided by the storage engines. That information is not accurate in some engines like InnoDB and they are based in statistics calculations therefore sometimes some tune is needed. In InnoDB these statistics are calculated automatically, check the following blog [...]
How FLUSH TABLES WITH READ LOCK works with Innodb Tables
March 23, 2012 By 20 Comments
Many backup tools including Percona Xtrabackup, MyLVMBackup and others use FLUSH TABLES WITH READ LOCK to temporary make MySQL read only. In many cases the period for which server has to be made read only is very short, just few seconds, yet the impact of FLUSH TABLES WITH READ LOCK can be quite large because [...]
Return of the Query Cache, win a Percona Live ticket
August 26, 2011 By 4 Comments
It’s Friday again, and time for another TGIF give-away of a Percona Live London ticket! But first, what’s new with the MySQL query cache? You may know that it still has the same fundamental architecture that it’s always had, and that this can cause scalability problems and locking, but there have been some important changes [...]
Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
I am constantly referring to the amazing MySQL manual, especially the option and variable reference table. But just as frequently, I want to look up blog posts on variables, or look for content in the Percona documentation or forums. So I present to you what is now my newest Firefox toolbar bookmark: an option and [...]
How fast is FLUSH TABLES WITH READ LOCK?
April 24, 2010 By 30 Comments
A week or so ago at the MySQL conference, I visited one of the backup vendors in the Expo Hall. I started to chat with them about their MySQL backup product. One of the representatives told me that their backup product uses FLUSH TABLES WITH READ LOCK, which he admitted takes a global lock on [...]
Paul McCullagh answers your questions about PBXT
November 20, 2009 By 2 Comments
Following on from our earlier announcement, Paul McCullagh has responded with the answers to your questions – as well as a few I gathered from other Percona folks, and attendees of OpenSQL Camp. Thank you Paul! What’s the “ideal” use case for the PBXT engine, and how does it compare in performance?  When would I [...]
Slow DROP TABLE
June 16, 2009 By 21 Comments
It is a known fact that ext3 is not the most efficient file system out there and for example file removals can be painfully slow and cause a lot of random I/O. However, as it turns out, it can sometimes have a much more severe impact on the MySQL performance that it would seem. When [...]
The perils of InnoDB with Debian and startup scripts
January 28, 2009 By 13 Comments
Are you running MySQL on Debian or Ubuntu with InnoDB? You might want to disable /etc/mysql/debian-start. When you run /etc/init.d/mysql start it runs this script, which runs mysqlcheck, which can destroy performance. It can happen on a server with MyISAM tables, if there are enough tables, but it is far worse on InnoDB. There are [...]
How Percona does a MySQL Performance Audit
November 24, 2008 By 17 Comments
Our customers or prospective customers often ask us how we do a performance audit (it’s our most popular service). I thought I should write a blog post that will both answer their question, so I can just reply “read all about it at this URL” and share our methodology with readers a little bit. This [...]
Concurrent inserts on MyISAM and the binary log
May 14, 2008 By 7 Comments
Recently I had an interesting surprise with concurrent inserts into a MyISAM table. The inserts were not happening concurrently with SELECT statements; they were blocking and the process list was filling up with queries in Locked status. My first thought was that the customer had deleted from the table, which leaves “holes” in the middle [...]
