The MySQL configuration file, e.g. /etc/my.cnf has a number of different section headings including [mysql], [mysqld], [mysqld_safe]. It is important that you ensure you put the right variables into the right section. For example, the following my.cnf configuration file will not operate as the user probably expects.

[mysqld]
...
log-bin=mysql-bin
server-id=1
query_cache_size = 100M
query_cache_type = 1

...

[mysqld_safe]
...
key_buffer_size=600M
skip-innodb
...

In this example, this configuration does not give you a MyISAM key buffer of 600M, it’s actually the default of 8M.

mysql> show global variables like 'key_buffer_size';
+-----------------+---------+
| Variable_name   | Value   |
+-----------------+---------+
| key_buffer_size | 8388600 |
+-----------------+---------+

Be sure to add the right options to the [mysqld] section.

What I didn’t know until yesterday was that some programs read from …

I hit this interesting problem last night on 5.0.51a.

mysql> use information_schema;
mysql> desc routines;
ERROR 1 (HY000): Can't create/write to file '/home/tmp/#sql_fea_1.MYD' (Errcode: 24)
mysql> show create table routines\G
*************************** 1. row ***************************
       Table: ROUTINES
Create Table: CREATE TEMPORARY TABLE `ROUTINES` (
  `SPECIFIC_NAME` varchar(64) NOT NULL default '',
  `ROUTINE_CATALOG` varchar(512) default NULL,
  `ROUTINE_SCHEMA` varchar(64) NOT NULL default '',
  `ROUTINE_NAME` varchar(64) NOT NULL default '',
  `ROUTINE_TYPE` varchar(9) NOT NULL default '',
  `DTD_IDENTIFIER` varchar(64) default NULL,
  `ROUTINE_BODY` varchar(8) NOT NULL default '',
  `ROUTINE_DEFINITION` longtext,
  `EXTERNAL_NAME` varchar(64) default NULL,
  `EXTERNAL_LANGUAGE` varchar(64) default NULL,
  `PARAMETER_STYLE` varchar(8) NOT NULL default '',
  `IS_DETERMINISTIC` varchar(3) NOT NULL default '',
  `SQL_DATA_ACCESS` varchar(64) NOT …

My talk on 10x performance improvements – A case study has just been approved for the 2010 MySQL Conference. This will be my 5th straight year speaking at the MySQL conferences. For those in Europe wanting a sneak peek I am also speaking at FOSDEM 2010 in Brussels on Feb 7th where I’ll be giving an abridged version.

As an independent MySQL consultant, my work generally covers performance tuning and scalability and sometimes database architecture. Often however my work involves a review of a given problem and recommendations (immediate, short and long term). I’m rarely involved in the full implementation and generally do not see the full fruits of the proposed work.

Recently however I was able to work with a client, first in resolving …

The Problem

I've had MySQL on my Windows 7 laptop for a bit (as part of wampserver), mostly for local offline WordPress development.

However, even though MySQL is relatively stable, I've been observing a vast quantity of intermittent MySQL errors, as reported by WordPress in the PHP error log (C:\wamp\logs\php_error.log). Here are some examples:

[05-Jan-2010 09:47:51] WordPress database error Error on delete of
'C:\Windows\TEMP\#sql17e0_1a2_6.MYD' (Errcode: 13) for query SELECT t.*, tt.* 
FROM wp_terms AS t INNER JOIN wp_term_taxonomy AS tt ON tt.term_id = t.term_id 
INNER JOIN wp_term_relationships AS tr ON tr.term_taxonomy_id = 
tt.term_taxonomy_id WHERE tt.taxonomy IN ('category') AND tr.object_id IN (3) 
ORDER BY t.name ASC made by require, require_once, include, get_footer, 
locate_template, load_template, require_once, dynamic_sidebar, 
call_user_func_array, …

For those in the US the annual MySQL UC is taking place again in April. For those in Europe we have dedicated room for MySQL and MySQL related products/variants/branches at FOSDEM 2010 being held in Brussels, Belgium on 6-7 Feb.

This conference will feature a full day of talks with a format of 20 minutes presentation and 5 minutes Q&A. More information about submissions can be found at Call for Papers for “MySQL and Friends” Developer Room at FOSDEM 2010 now open!

Other references:

• FOSDEM 2010 (via Forge Wiki)
• …

Normally I like to use the OS’s package manager to manage the software on my system. This ensures that things are done consistently. When managing MySQL I’d also like to manage all my instances the same way. That makes life easier for me but also for my fellow DBAs and sysadmin colleagues.

I use CentOS and the rpm packages it provides and these work quite well. However, the MySQL rpms do not allow me to manage single and multiple instances alike and while mysqld runs as the mysql user the instance management needs to be done as root (stopping, starting instances, or default access). If you want to run multiple instances you can also use mysqld_multi, but that’s not the default setup.

So this is not ideal. While this may not be much of an issue if you manage a single server, if you manage tens or …

MySQL has an unusual grants system that allows a user to be specified by host, ip or network address. That is you identify a user as ’some_user’@'host.host.name’, ’some_user’@'1.2.3.4′ or ’some_user’@'10.3.%’.

That is quite a nice facility but using it is rather tricky. This potentially provides a lot more security as it allows you to specify that different types of database users can only perform certain actions from different types of hosts. So even if you know the user and password you may have trouble getting into a mysqld server. That’s good.

However, this flexibility comes at a price. There are no tools to help you manage this and I have often seen people resorting to using the simplest type of grant, for some_user@’%', or some_user@’10.%’.

I recently wrote a smalltemplate script which would allow me to …

When looking at a set of SQL statements in isolation with tools such as the slow query log, processlist and tcpdump/mk-query-digest it is easy to identify queries that are slow.

It is more difficult however to identify the frequency of the query, and whether the slow query is actually acceptable in your overall system design.

I very simple technique to help you is to comment your queries. For example:

SELECT /* 10m cache */ ...;

When I’m working for a client, this process enables me to realize the purpose of the query more quickly and to help prioritize which queries I need to improve first. This does not mean I simply ignore these less frequent queries, however my choices for reviewing and indexing queries on given tables is adjusted generally for OLTP queries first, and batch second.

As with all practices it is important to implement across your full code base.

It finally dawned on me while reflecting on the year past this Sunday that the missing voice since the announcement of the Oracle acquisition of Sun Microsystems (and therefore MySQL) has been the MySQL employees.

When I worked as an employee for MySQL Inc, the acquisition by Sun Microsystems in 2008 lead to several requirements about the acquisition.

• You were not allowed to talk about the acquisition publically.
• You were not allowed to communicate with any Sun (i.e. the acquirer) resources.

In other words it was “business as usual” which is really an oxymoron, because business will never be exactly as it was before the announcement. The ongoing delay in pending acquisition by Oracle Corporation is really hurting everybody with getting on with doing their jobs, being happy with their work, and making a difference in open source and in the lives of all the benefit from using MySQL.

…

I have had a busy year playing with databases and it is nice that now things are slowing down. Of course next year holds lots more changes, but that is normal.

The big MySQL 5.0 to 5.1 upgrade that I have been spending a lot of time on recently has nearly finished. In spite of the early issues with upgrading servers with stored procedures and triggers, most of the servers are now running 5.1 so that is good, and the upgrades have been reasonably painless. Only the master servers need to be looked at, but with fewer people being around over the holiday period this will wait until next year.

Several users have been pleasantly surprised by the performance gain in switching to 5.1. That is also good news. When I finish upgrading all servers I will also be able to try out some of the 5.1 features such as RBR or partitioning. On the larger servers I’m hoping this will further help performance.

Finally I should be able to escape …