mysql

The following maintenance jobs are typically run against a MySQL database:

• Backup
• Clean-up binary logs
• Optimize tables
• Purge query cache
• Rotate binary logs

Backup

A backup is not a typical maintenance job. But it behaves more or less like one. The backup should be done regularly depending on the restore/PITR (Point in Time Recovery) requirements.

According to Johans wishes I write down my concerns about MySQL (Cluster) replication. These items are things I run again and again into it with customers:

Sometimes it is nice to show customers the functionality of MySQL-Enterprise Monitor (aka Merlin). I install the agents on the servers and the dashboard runs on my laptop. But very often only ssh is open to these servers.

So how to dig a whole through the firewall for MySQL-Enterprise Monitor?

# ssh -R 18080:localhost:18080 oli@where_the_agent_sits

Maybe trivial for you but for me its hard to remember...

A friend of me asked me long time ago: "How can I have a ranking on a result with MySQL?". Now I found some time to write it down:

Lets do first some preparation for the example:

CREATE TABLE sales (
  id     INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY
, fruit  VARCHAR(32)
, amount DECIMAL
);

INSERT INTO sales
VALUES (NULL, 'apple', 12.75), (NULL, 'orange', 1.89), (NULL, 'pear', 19.23)
     , (NULL, 'banana', 4.25), (NULL, 'cherry', 123.75), (NULL, 'plum', 23.15)
;

Now lets query:

With MySQL 5.0 the database provides trigger functionality on INSERT, REPLACE, UPDATE and DELETE.

Those of you who know some other RDBMS know, that there are also some system events where one would like to have triggers.

Unfortunately MySQL does not (yet) provide such functionality. This is sad because as database administrator this would be sometimes very helpful.

But you can build your own LOGON and STARTUP trigger.

MySQL provides some hooks for these events...

Recently the question came up if it is faster to restore a MySQL cluster when all nodes are up or only ONE node from each node group during restore.

The answer from our gurus was: All nodes up during restore! I wanted to find out why. So I set up the following cluster and started to measure:

MySQL Cluster set up

It is possible to use an active - active shared-disk cluster in MySQL in some cases. For doing this you have to fulfill the following requirements:

In a round-robin database (RRD) usually time-series data like network bandwidth, temperatures, CPU load etc. is stored. The data is stored in the way that system storage footprint remains constant over time. This avoids resource expensive purge jobs and reduces complexity.

MySQL does NOT yet provide this kind of storage engine. Although some people were thinking about and some prototypes exists.

Probably the answer to this question is already known. But we want to prove it and by the way learn to deal with MySQL and oprofile.

Materialised View (MV) is the pre-calculated (materialised) result of a query. Unlike a simple VIEW the result of a Materialised View is stored somewhere, generally in a table. Materialised Views are used when immediate response is needed and the query where the Materialised View bases on would take to long to produce a result. Materialised Views have to be refreshed once in a while. It depends on the requirements how often a Materialised View is refreshed and how actual its content is.

We have added some more tools to our MySQL consulting tools collection.

We have added some more database benchmarks to our collection.

More details you can find on our Benchmarking page.

One of the big advantages of MySQL is its concept of pluggable Storage Engines (SE). This means you can choose the most optimal storage engine for your needs. This also has a disadvantage: You have to know what you are doing...

More details you can find here: MySQL pluggable Storage Engines (SE).