April 21, 2014

Solving INFORMATION_SCHEMA slowness

Many of us find INFORMATION_SCHEMA painfully slow to work it when it comes to retrieving table meta data. Many people resort to using file system tools instead to find for example how much space innodb tables are using and things like it. Besides being just slow accessing information_schema can often impact server performance dramatically. The […]

Optimizing slow web pages with mk-query-digest

I don’t use many tools in my consulting practice but for the ones I do, I try to know them as best as I can. I’ve been using mk-query-digest for almost as long as it exists but it continues to surprise me in ways I couldn’t imagine it would. This time I’d like to share […]

Tools

This page contains links to various tools we found helpful to use in practice. Some tools are written by us, others by third parties, yet another ones may be shipped with your operating system you just need to find they are there. Percona Toolkit Percona Toolkit is a great set of tools for MySQL Performance […]

Microslow patch for 5.0.37

Just short message that patch enables microsecond resolution in slow-log (see more http://www.mysqlperformanceblog.com/2006/09/06/slow-query-log-analyzes-tools/) for 5.0.37 is available here: www.mysqlperformanceblog.com/files/patches/patch.slow-micro.5.0.37.diff The patch for 5.0.41 : www.mysqlperformanceblog.com/files/patches/patch.slow-micro.5.0.41.diff

MySQL Slow query log in the table

As of MySQL 5.1 get MySQL slow query log logged in mysql.slow_log table instead of the file as you had in previous versions. We rarely would use this feature as it is incompatible with our slow query analyses patch and tools Fixing this is not trivial while staying 100% compatible to standard format as TIME […]

MySQL Replication and Slow Queries

I just filed a bug regarding slow queries executed by replication thread are not being logged to the slow query log. This is not a big deal but it is ugly little gotcha which I think few people know about. It is especially bad if you’re using tools to analyze slow query log to find […]

Many-table joins in MySQL 5.6

I recently worked on an uncommon slow query: less than 100 rows were read and returned, the whole dataset was fitting in memory but the query took several seconds to run. Long story short: the query was a join involving 21 tables, running on MySQL 5.1. But by default MySQL 5.1 is not good at […]

DBA 101: Sometimes forgotten functionality in the MySQL client

The MySQL client has some functionalities some of us never use. Why would you use them and what is the added value of this? Every DBA and developer has had a moment when he or she needs to connect to a MySQL database using the command line tool. Therefore I’ve written down an explanation of […]

Analyzing WordPress MySQL queries with Query Analytics

This blog, MySQLPerformanceBlog.com, is powered by WordPress, but we never really looked into what kind of queries to MySQL are used by WordPress. So for couple months we ran a Query Analytics (part of Percona Cloud Tools) agent there, and now it is interesting to take a look on queries. Query Analytics uses reports produced […]

2 cases for MySQL server overload

Your MySQL server is overloaded. You see hundreds of running queries in the SHOW PROCESSLIST taking many seconds to run, or can’t connect at all because all connections slots are busy. If you have worked with MySQL long enough you surely have seen it, probably more than once. This is what I would call “MySQL […]