April 23, 2014

Tools and tips for analysis of MySQL’s Slow Query Log

MySQL has a nice feature, slow query log, which allows you to log all queries that exceed a predefined about of time to execute. Peter Zaitsev first wrote about this back in 2006 – there have been a few other posts here on the MySQL Performance Blog since then (check this and this, too) but […]

What kind of queries are bad for MySQL?

In writing a recommendation for our Web development team on how to use MySQL, I came up with the following list, which I want to share: What kind of queries are bad for MySQL? Any query is bad. Send a query only if you must. (Hint: use caching like memcache or redis) Queries that examine […]

Percona Server for MySQL 5.5.30-30.2 now available

Percona is glad to announce the release of Percona Server for MySQL 5.5.30-30.2 on April 10, 2013 (Downloads are available here and from the Percona Software Repositories). Based on MySQL 5.5.30, including all the bug fixes in it, Percona Server 5.5.30-30.2 is now the current stable release in the 5.5 series. All of Percona‘s software is open-source and free, all the details of […]

Understanding the maximum number of columns in a MySQL table

This post was initially going to be two sets of polls: “What is the maximum number of columns in MySQL?” and “What is the minimum maximum number of columns in MySQL?”. Before you read on, ponder those questions and come up with your own answers… and see if you’re right or can prove me wrong! […]

Unexpected problem with triggers and mysqldump

Some time ago, I had to convert all tables of a database from MyISAM to InnoDB on a new server. The plan was to take a logical dump on the master, exporting separately the schema and the data, then edit the CREATE TABLE statements to ensure all tables are created with InnoDB, and reload everything […]

Replication of the NOW() function (also, time travel)

Notice the result of the NOW() function in the following query. The query was run on a real database server and I didn’t change the clock of the server or change anything in the database configuration settings.

You may proceed to party like it is 1999. How can the NOW() function return a value […]

FOSDEM 2012 – MySQL and Friends devroom

2012 is near… and so is the next FOSDEM edition ! This year again, MySQL will be represented by its Community. If you want to discuss with friend’s of MySQL it’s the place to be in February ! Like every year, FOSDEM takes place the first week-end of February in Brussels. The MySQL and Friends […]

Getting History of Table Sizes in MySQL

One data point which is very helpful but surprisingly few people have is the history of the table sizes. Projection of data growth is very important component for capacity planning and simply watching the growth of space used on partition is not very helpful. Now as MySQL 5.0+ has information schema collecting and keeping this […]

MySQL Performance – eliminating ORDER BY function

One of the first rules you would learn about MySQL Performance Optimization is to avoid using functions when comparing constants or order by. Ie use indexed_col=N is good. function(indexed_col)=N is bad because MySQL Typically will be unable to use index on the column even if function is very simple such as arithmetic operation. Same can […]

Measuring Max Replication Throughput on Percona XtraDB Cluster with wsrep_desync

Checking throughput with async MySQL replication Replication throughput is the measure of just how fast the slaves can apply replication (at least by my definition).  In MySQL async replication this is important to know because the single-threaded apply nature of async replication can be a write performance bottleneck.  In a production system, we can tell […]