While testing MySQL 5.6, I came across some curious values for the new values used to set the crash-safe slave tables. To get safety, we need to set relay_log_info_repository and master_info_repository to 'TABLE'. That way, the replication information, instead of going to a file, will be saved to two tables in the mysql schema (mysql.slave_relay_log_info and mysql.slave_master_info).

So I was setting these values back and forth between 'FILE' and 'TABLE', until I made a "mistake." Instead of typing

set global relay_log_info_repository='table';

I wrote

set global relay_log_info_repository=1;

MySQL, like a lot of other software, has many knobs you can tweak. Most of these knobs may affect behaviour, but more importantly most affect the memory usage of the server, so getting these settings right is very important.

Most of MySQL’s memory is really used just as a cache, in one form or another, information that otherwise is on disk. So ensuring you have as large a cache as possible is important. However, making these memory sizes too large will trigger the server to start swapping and possibly can cause it to crash or cause the kernel to kill the process when it runs out of memory.  So that’s something we want to avoid.

Certain settings affect memory allocation on a per connection/thread basis, being bounded by thread_cache_size and max_connections.  If you configure for the worst behaviour (max_connections) you may end up not actually using all

GRANT INSERT,DELETE,UPDATE on world.* to myuser identified by 'mypass';
GRANT SELECT on world.* to myuser identified by 'mypass' WITH GRANT OPTION;
show grants for myuser\G
*************************** 1. row ***************************
Grants for myuser@%: GRANT USAGE ON *.* TO 'myuser'@'%' IDENTIFIED BY PASSWORD '*6C8989366EAF75BB670AD8EA7A7FC1176A95CEF4'
*************************** 2. row ***************************
Grants for myuser@%:

IOUG has a free series of three webinars on upgrading MySQL. Each webinar is an hour long, and it starts with a webinar by me tomorrow at 12 noon Central time (GMT-5) on “Why and How to Upgrade to MySQL 5.1″. The webinar assumes you are upgrading from MySQL 5.0 to MySQL 5.1, and talks a little bit about the new features, server variables, and what you need to know when upgrading to MySQL 5.1.

The software used is GoToWebinar (formerly GoToMeeting), so you will need to install that software. To register, use the links on the IOUG MySQL Upgrade Webinar Series page.

The complete list of webinars in the MySQL Upgrade Series is:
* MySQL 5.1: Why and How to Upgrade
Sheeri Cabral, The Pythian Group
Tuesday, July 27, 12:00 p.m. – 1:00 p.m. CT (GMT-5)

While setting up MySQL Enterprise Monitor (http://www.mysql.com/products/enterprise/monitor.html" target="_blank) 2.2 (Merlin) on a system which had been running version 2.1 I thought I’d try and see what difference the change from using normal innodb tables to using the compressed table format available in the innodb plugin.

I’ve been using a separate db backend for merlin because for me it’s easier to manage and also the database backend has been put on a dedicated server. I’ve also been trying the innodb_plugin on another busier server as I had performance problems with the normal 5.1.42 built-in innodb engine which the plugin managed to solve.

So given that I was using a separate db server I upgraded it to 5.1.47, configured the server to use

TO_DAYS() prunes two partitions instead of one

I have been upgrading more MySQL database instances recently and have found a few more potential gotchas, which if you are not careful, can potentially be rather nasty. These are not documented explicitly by MySQL, so it may be handy for you to know if you have not come across this type of thing before.

Most of the issues are those related to upgrading MySQL instances which are replicated, either the master servers or the slaves. Some seem specific to the rpm packages I am using (MySQL enterprise or MySQL advanced rpms), though others are not.

Take care upgrading a 5.0 master when you have 5.1 slaves

It is not a good idea to run a mixed major version of mysql in a replicated environment so why would I be doing this? If you work in a replicated environment and have several slaves then it is recommended that you upgrade the slaves first. I work with quite

As part of reviewing storage engines for my work on the upcoming Expert PHP and MySQL book, I finally had an excuse to try out the InnoDB Plugin for MySQL which is now conveniently included with MySQL 5.1 since 5.1.38.

Following the MySQL 5.1 Reference Manual instructions at 13.6. The InnoDB Storage Engine I included the bare minimum as documented to my my.cnf.

[mysqld]
ignore-builtin-innodb
plugin-load=innodb=ha_innodb_plugin.so ;innodb_trx=ha_innodb_plugin.so ;innodb_locks=ha_innodb_plugin.so ;innodb_cmp=ha_innodb_plugin.so ;innodb_cmp_reset=ha_innodb_plugin.so ;innodb_cmpmem=ha_innodb_plugin.so ;innodb_cmpmem_reset=ha_innodb_plugin.so

However to my misfortune the following error occured.

091212 17:45:14

According to the official lifecycle calendar at http://www.mysql.com/about/legal/lifecycle/#calendar (http://www.mysql.com/about/legal/lifecycle/#calendar), active support for MySQL 5.0 (including regular binary updates) will end on December 31st, 2009, which is about 3 weeks away.

Many folks are still using MySQL 5.0.45, as until October that was the package that came with RedHat. That was released in July 2007, over 2 years ago!

Upgrading to MySQL 5.1 is not difficult, though it requires more steps than just upgrading the packages.

There is a list with all the changes made that might affect the upgrade process at http://www.pythian.com/news/1414/new-in-mysql-51-sheeris-presentation/. This includes which variable names have been deprecated and changed, as well as how

It’s been a while since I’ve posted anything new. In the meantime I’ve been pretty busy. Working on production systems often means that you are not running bleading edge. That’s fine but sometimes you need to look at doing the upgrade and to do that you have to do quite a few checks to see how well newer versions of the software you use will work.

I’ve been in that situation with MySQL. I have quite a few boxes most of which are 5.0 and have been working fine. MySQL-5.1 has been GA now for some time, and I have started to look at it as support for 5.0 is about to end.  I’ve already found quite a few 5.1 bugs, good enough to crash the server, but again that’s to be expected. Heavy loads and odd usage of the server means that MySQL can never be able to test all things.  Replication problems caused a few issues with the

USE test;
DROP TABLE IF EXISTS users;

CREATE TABLE users (

The server

$ cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5.2 (Tikanga)

 select version();
+-----------+
| version() |
+-----------+
| 5.1.32    | 
+-----------+
1 row in set (0.00 sec)

 set global server_id =inet_aton('192.168.2.55');
Query OK, 0 rows affected (0.00 sec)

 select @@server_id;