August 21, 2014

max_allowed_packet and binary log corruption in MySQL

The combination of max_allowed_packet variable and replication in MySQL is a common source of headaches. In a nutshell, max_allowed_packet is the maximum size of a MySQL network protocol packet that the server can create or read. It has a default value of 1MB (<= 5.6.5) or 4MB (>= 5.6.6) and a maximum size of 1GB. […]

Schema changes – what’s new in MySQL 5.6?

Among many of the improvements you can enjoy in MySQL 5.6, there is one that addresses a huge operational problem that most DBAs and System Administrators encounter in their life: schema changes. While it is usually not a problem for small tables or those in early stages of product life cycle, schema changes become a […]

MySQL opening .frm even when table is in table definition cache

or… “the case of Stewart recognizing parameters to the read() system call in strace output”. Last week, a colleague asked a question: I have an instance of MySQL with 100 tables and the table_definition_cache set to 1000. My understanding of this is that MySQL won’t revert to opening the FRM files to read the table […]

Reasons for MySQL Replication Lag

One common theme in the questions our MySQL Support customers ask is MySQL Replication Lag. The story is typically along the lines everything is same as before and for some unknown reason the slave is started to lag and not catching up any more. I always smile at “nothing has changed” claim as it usually […]

High availability for MySQL on Amazon EC2 – Part 2 – Setting up the initial instances

This post is the second of a series that started here. The first step to build the HA solution is to create two working instances, configure them to be EBS based and create a security group for them. A third instance, the client, will be discussed in part 7. Since this will be a proof […]

Copying InnoDB tables between servers

The feature I announced some time ago http://www.mysqlperformanceblog.com/2009/06/08/impossible-possible-moving-innodb-tables-between-servers/ is now available in our latest releases of XtraBackup 0.8.1 and XtraDB-6. Now I am going to show how to use it (the video will be also available on percona.tv). Let’s take tpcc schema and running standard MySQL ® 5.0.83, and assume we want to copy order_line […]

How to check MySQL Config files

Probably most of MySQL users sometime had a situation when they would do changes in MySQL config file without restarting server (may be matching SET GLOBAL command to do it in run time) but either because option is misspelled or because given version does not support such option the server when would refuse to start […]

10+ Ways to Crash or Overload MySQL

People are sometimes contacting me and asking about bugs like this which provide a trivial way to crash MySQL to the user with basic privileges and asking me what to do. My answer to them is – there is nothing new to it and they just sit should back and relax Really – there are […]

Percona XtraBackup 2.1.9 is now available

Percona is glad to announce the release of Percona XtraBackup 2.1.9 on May 7th, 2014. Downloads are available from our download site here and Percona Software Repositories. This release is the current GA (Generally Available) stable release in the 2.1 series. Percona XtraBackup is an open source, free MySQL hot backup software that performs non-blocking […]

WITHer Recursive Queries?

Over the past few years, we’ve seen MySQL technology advance in leaps and bounds, especially when it comes to scalability. But by focusing on the internals of the storage engine for so long, MySQL has fallen behind regarding support for advanced SQL features. SQLite, another popular open-source SQL database, just released version 3.8.3, including support […]