Before I forget it and have to search again here a short note about how to rename a MySQL Partition:

My dream:

ALTER TABLE history RENAME PARTITION p2015_kw10 INTO p2015_kw09;

ALTER TABLE history
REORGANIZE PARTITION p2015_kw10 INTO (
PARTITION p2015_kw09 VALUES LESS THAN (UNIX_TIMESTAMP('2015-03-02 00:00:00'))
);

Caution: REORGANIZE PARTITION causes a full copy of the whole partition!

MySQL Enterprise Backup (MEB) has the capability to make real incremental (differential and cumulative?) backups. The actual releases are quite cool and you should really look at it...

Unfortunately the original MySQL documentation is much too complicated for my simple mind. So I did some testing and simplified it a bit for our customers...

MySQL Enterprise Monitor (MEM) has by default no Event Handlers created and activated. These Event Handlers you have to define yourself according to your needs.

FromDual has the pleasure to announce the release of the new version 1.0.0 of its widely used Nagios and Icinga plugins for MySQL, Galera Cluster, MariaDB and Percona Server.

All plugins are basically renewed and should now work all correctly.

The new Nagios/Icinga plugins can be downloaded here.

In the inconceivable case that you find a bug in the Nagios/Icinga plugins please report it to our bug tracker.

MySQL provides some great enterprise features beside the MySQL Server. The ones we are asked the most at customers are:

Sometimes we face the situation where we have a full MySQL database backup done with mysqldump and then we have to restore and recover just one single table out of our huge mysqldump file.
Further our mysqldump backup was taken hours ago so we want to recover all the changes on that table since our backup was taken up to the end.

In this blog article we cover all the steps needed to achieve this goal for MySQL and MariaDB.

We recently run into some troubles with max_allowed_packet size problems during backups with the FromDual Backup/Recovery Manager and thus I investigated a bit more in the symptoms of such problems.

Read more about: max_allowed_packet.

For processing SELECT queries MySQL needs some times the help of temporary tables. These temporary tables can be created either in memory or on disk.

The number of creations of such temporary tables can be found with the following command:

After properly installing and testing a Galera Cluster we see that the set-up is not finished yet. It needs something in front of the Galera Cluster that balances the load over all nodes.

We have recently seen a case where the following command was executed on a Galera Cluster node:

Precaution: Before you try this out on your production system do a BACKUP first! FromDual Backup Manager can help you with this.

Situation

A MySQL user has delete its InnoDB table files for example like this:

shell> rm -f $datadir/test/test.*

Analysis

We do some analysis first:

This week, we did some migrations from MariaDB 10.0 to Percona Server 5.6 at the IT department of a big German bank.

We were perfectly aware that since version 10.0 the MariaDB code base started to diverge slightly away from the MySQL and Percona Server code base which are still pretty close to each other.

Because of the Percona Server option enforce_storage_engine we wanted to do this migration.

Sometimes it could be desirable to replicate from a Galera Cluster to a single MySQL slave or to an other Galera Cluster. Reasons for this measure could be:

MySQL single query performance - the truth!

As suggested by morgo I did a little test for the same query and the same data-set mentioned in Impact of column types on MySQL JOIN performance but looking into an other dimension: the time (aka MySQL versions).

The answer

To make it short. As a good consultant the answer must be: "It depends!" :-)

In our MySQL trainings and consulting engagements we tell our customers always to use the smallest possible data type to get better query performance. Especially for the JOIN columns.

Great News: Galera Cluster v3.1 GA for MySQL 5.6 was released at Percona Live London (PLUK) 2013. The information is still a bit hidden...

You can find it here:

We had a Galera Cluster support case recently. The customer was drenched in tears because his Galera Cluster did not work any more and he could not make it work any more.

Upsss! What has happened?

A bit of the background of this case: The customer wanted to do a rolling-restart of the Galera Cluster under load because of an Operating System upgrade which requires a reboot of the system.

Lets have a look at the MySQL error log to see what was going on. Customer restarted server with NodeC:

In MySQL we have the typical behaviour that we open and close connections very often and rapidly. So we have very short-living connections to the server. This can lead in extreme cases to the situation that the maximum number of TCP ports are exhausted.

The maximum number of TCP ports we can find with:

# cat /proc/sys/net/ipv4/ip_local_port_range
32768   61000

In this example we can have in maximum (61000 - 32768 = 28232) connections concurrently open.

It took me quite a while to find out how the beast Galera Arbitrator (garbd) works. To safe your time here a short summary:

Our bigger customers where we help to deploy Galera Cluster for MySQL set-ups have some commercial hardware (e.g. F5 or Cisco) for load balancing instead of software load balancers.

Recently a forum question [ 1 ] got my attention:

Is there any performance issue with Union?

I used union all sometime back and it was performance issue just to make an opinion that we should used union in query.

Maybe you experienced some strange behaviour with MySQL: Everything is installed correctly and should work. But it does not.

Symptoms we have seen:

Recently we had to set-up a 3-node Galera Cluster with a Load Balancer in front of it. Because Galera Cluster nodes (mysqld) still reply to TCP requests on port 3306 when they are expelled from the Cluster it is not sufficient to just leave it to the Load Balancer to check the port if a Galera node is properly running or not.

Switching from MySQL/MyISAM to Galera Cluster requires that all tables (except those from the mysql, information_schema and performance_schema) are using the InnoDB Storage Engine.

For altering the Storage Engine of the tables we wrote a script (alter_engine.pl) long time ago already. Because we have made many of those switches recently we have extended its functionality.

From time to time some maintenance work on the MySQL database has to be done. During the maintenance window we do not want to have application traffic on the database.

Sometimes it is hard to shut down all applications spread over the whole company. Or we want to allow only some specific hosts to access mysql from remote (for example the monitoring system or the backup server).

For this purpose we can use the Linux packet filtering.

To see what packet filtering rules are available we can run the following command: