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 [...]
Checking for a live database connection considered harmful
May 5, 2010 By 38 Comments
It is very common for me to look at a customer’s database and notice a lot of overhead from checking whether a database connection is active before sending a query to it. This comes from the following design pattern, written in pseudo-code:
1 2 3 4 5 6 | function query_database(connection, sql) if !connection.is_alive() and !connection.reconnect() then throw exception end return connection.execute(sql) end |
Many of the popular development platforms do something similar to this. Two [...]
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 [...]
Mass killing of MySQL Connections
May 21, 2009 By 30 Comments
Every so often I run into situation when I need to kill a lot of connections on MySQL server – for example hundreds of instances of some bad query is running making server unusable. Many people have special scripts which can take the user, source host or query as a parameter and perform the action. [...]
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 [...]
Using MMM to ALTER huge tables
March 27, 2008 By 11 Comments
Few months ago, I wrote about a faster way to do certain table modifications online. It works well when all you want is to remove auto_increment or change ENUM values. When it comes to changes that really require table to be rebuilt – adding/dropping columns or indexes, changing data type, converting data to different character [...]
Filtered MySQL Replication
November 7, 2007 By 8 Comments
To get this straight – I’m not a big fan of filtered or partial MySQL Replication (as of version MySQL 5.0) – there is enough gotchas with replication itself and getting things right with filtering can get quite bumpy road. In some applications however it is very helpful so lets see what one should do [...]
Microslow patch for 5.1.20
July 18, 2007 By 3 Comments
Microslow patch has been there for some time, but only for earlier MySQL editions such as 4.1 and 5.0. Now it’s also available for the latest 5.1. Because MySQL went through a lot of internal changes, the patch had to be written from scratch. It introduces some minor change in existing functionality and also adds [...]
MySQL Server Memory Usage
May 17, 2006 By 21 Comments
Every so often people ask me the question how should they estimate memory consumption by MySQL Server in given configuration. What is the formula they could use. The reasons to worry about memory usage are quite understandable. If you configure MySQL Server so it uses too small amount of memory it will likey perform suboptimally. [...]
