Next time you have an error whilst running an sql script into mysql using the pretty easy redirect into eg: mysql -uroot -pmsandbox -h127.0.0.1 -P3306 dbname < filename you might want to give the -v option a shot.

MySQL normally outputs an error with the line number like:

[mysql@dcassar-ubuntu /mysql/dumps/stored_procs 11:10:12]$ mysql -uroot -pmsandbox -h127.0.0.1 -P5151 test < file
ERROR 1267 (HY000) at line 375: Illegal mix of collations (latin1_swedish_ci,IMPLICIT) and (latin1_general_cs,IMPLICIT) for operation '='


But 375 is not including comments and stuff so it’s a bit hard to go through the file to locate the exact section which is failing.

Run the same command with -v:

[mysql@dcassar-ubuntu /mysql/dumps/stored_procs 11:10:30]$ mysql -uroot -pmsandbox -h127.0.0.1 -P5151 -v test < file | tail -5
ERROR 1267 (HY000) at line 375: Illegal mix …

In the last post, we saw how to create a test OpenLDAP server, populate it and secure it with SSL certificates. Now we are going to have a look at how to configure MySQL Enterprise Manager (MEM) to authenticate against LDAP. We will be examining a few different kinds of setup methods.

1. Using LDAP to fetch just the user password

The simplest form is to configure a user with MEM and set it to the LDAP type. The user’s role is setup in MEM during user creation time and is not fetched from LDAP. Below you can see the user definition page:

How to create a LDAP user in MEM - password only

The username is user1 as specified in MEM, but where do we get the password …

The latest 2.2 release of MySQL Enterprise Monitor (MEM) has the ability to authenticate against LDAP. I decided to test this setup and for that, I had to create and populate an OpenLDAP server, including STARTTLS/SSL certificates. This guide was done on CentOS 5.5 but it shouldn’t be much different in other Linux/Unix distributions. First, start off by installing the packages with:

root@shell> yum install openldap openldap-clients openldap-servers

Then head to /etc/openldap where you can set you domain and the DN for the LDAP manager user. I’ve inserted some useful comments into the slapd.conf file. Lines without comments have not been changed from the default slapd.conf file.

shell> grep -v "^#" /etc/openldap/slapd.conf | grep -v "^$"
include         /etc/openldap/schema/core.schema
include         /etc/openldap/schema/cosine.schema
include         /etc/openldap/schema/inetorgperson.schema
include …

With the release of MySQL Enterprise Monitor (MEM) 2.2, there is now the ability to monitor queries using the Query Analyzer (QUAN) without needing the agent proxy to be running. You can use a .NET or JDBC connector plugin to directly gather the query statistics. In the example below, we will use the MySQL Enterprise Plugin for Connector/J.

First, make sure both the Connector/J, the Connector/J plugin and the Apache Commons Logging jars are in the $CLASSPATH. At the time of writing, these are the files needed:

mysql-connector-java-5.1.12-bin.jar
c-java-mysql-enterprise-plugin-1.0.0.42.jar
required/commons-logging-1.1.1.jar

Then, add the plugin to the connection string so that it changes from something like this:

conn = …

Seeing as it looks like 5.5 is shortly about to go GA I thought I’d give it a run and see how well it works. The only way really to test it is to give it a bit of load and look for things which break. That I did with the 5.5.6-rc community rpms, compared to the 5.1 advanced rpms I usually run.

My colleagues, Ben and Peter, found a horrible problem which means that I can’t use this even for any real usage on my real servers. See: bug#57095 for all the gory details. Thanks to them both for finding the problem and then digging down and figuring out the real cause. Sometimes developers work a long way from the database so their errors don’t translate into something I can really look at in the database. They delved into the problem and then found the cause and a nice easy test case which I could report to MySQL.

After a couple of days of running this was …

I collect a lot of configuration values from my database servers and most of these values are stored by date.

So often I end up with values such as:


config_date config_value
2010-09-01  value_1
2010-09-02  value_1
2010-09-03  value_2
2010-09-04  value_3
2010-09-05  value_3
2010-09-06  value_3
2010-09-07  value_3
2010-09-08  value_4
2010-09-09  value_4
2010-09-10  value_1
2010-09-11  value_5
2010-09-12  value_5
2010-09-13  value_5
I´ve been unsuccessfully been trying to figure out how to convert this in SQL into something like the following:


config_from config_to   config_value
2010-09-01  2010-09-02  value_1
2010-09-03  2010-09-03  value_2
2010-09-04  2010-09-07 …

I was recently struck by a problem which is unusual. In order to keep an eye on the database server I use nagios, cacti, merlin and some local scripts to monitor the database instance and ensure that it is working properly.  That normally works fine.  The different monitor processes do various things, one of which is to monitor the replication status of a slave, and warn me if the replication is not working or if it’s behind. This is done with the command SHOW SLAVE STATUS.

The server I was looking at runs some large local batch jobs aggregating data. Unfortunately, I was experiencing that replication was interfering with these batch jobs so decided to see if things would perform better if I stopped replication and let the batch …

This has really been a long debate as to which approach is more performance orientated, normalized databases or denormalized databases. So this article is a step on my part to figure out the right strategy, because neither one of these approaches can be rejected outright. I will start of by discussing the pros and cons of both the approaches. Pros and Cons of a Normalized database design. Normalized databases fair very well under conditions where the applications are write-intensive and the write-load is more than the read-load. This is because of the following reasons: Normalized tables are usually smaller and...

With OpenSQL Camp and FrOSCon being over for almost a week now, it's time to come up with a short summary. I traveled home on Monday morning and then took Tuesday off, so I had some catching up to do...

As for the past years, FrOSCon rocked again! According to the closing keynote, they had around 1.500 (unique) visitors and I had a great time there. I really enjoyed meeting all the old and new faces of the various Open Source communities. The lineup of speakers was excellent, Jon "maddog" Hall's keynote about "Free and Open Source Software in the Developing World" was quite insightful and inspiring.

Most of the time I was busy with speaking at and …

The Problem

Developers often need to have a development database copy of the live production system you are using in able to allow them to test their code and to test new functionality and make schema changes to the database for this new functionality to work.

That’s normal and happens everywhere. A typical DBA task is to make a copy of the live system, sometimes to remove any confidential or sensitive information which perhaps the development database users should not be able to see, and then give them access to this development instance. The developers then “hack away”, changing their code and perhaps things in the database until they are ready to put these new changes into production when they then come along and discuss how to apply these changes into the live systems.

Once the development database has been created it soon becomes stale so often the developers want a new up to date copy …