MySQL uses locks for concurrency control. Whenever a client/thread acquires a lock, it will have exclusive access to that table or row (depending on the granularity of the lock). Other clients however, will be prevented from writing and possibly reading to/from the locked resource. The two main existing locks are:

READ LOCK – A read lock will allow the other clients to read from the locked resource but not write to it.
WRITE LOCK – a write lock will prevent the other clients from reading or writing to the locked resource.

Also, different storage engines have different lock granularity. For example, MyISAM will lock the whole table while InnoDB will only lock the rows it needs.

Let’s try this out using a MyISAM table. We open two concurrent sessions and in the first lock the City table from the world database (get it …

This week I will be the moderator for a MySQL Webinar How to secure MySQL data and achieve PCI compliance being held Thursday, September 11, 2008, 10:00 am PST, 1:00 pm EST, 18:00 GMT.

Recently I wrote about Do you store credit cards in your MySQL Database?. If you do, then PCI Compliance is not something you can ignore.

This webinar will not only be discussing PCI Compliance, but also MySQL data security. Our panel includes Didier Godart from MasterCard Worldwide, one of three members who drafted the Payment Card Industry Data Security Standard 1.0.

For more information on the various PCI Compliance and Encryption options for MySQL , check out the …

Slave delay can be a nightmare. I battle it every day and know plenty of people who curse the serialization problem of replication. For those who are not familiar with it, replication on MySQL slaves runs commands in series – one by one, while the master may run them in parallel. This fact usually causes bottlenecks. Consider these 2 examples:

• Between 1 and 100 UPDATE queries are constantly running on the master in parallel. If the slave IO is only fast enough to handle 50 of them without lagging, as soon as 51 start running, the slaves starts to lag.
• A more common problem is when one query takes an hour to run (let's say, it's an UPDATE with a big WHERE clause that doesn't use an index). In this case, the query runs on the master for an hour, which isn't a big problem because it doesn't block other queries. However, when the query moves over to the slaves, all of them start to lag because it plugs up the single …

One of the sessions at DrupalCon I attended was Larry Garfield's talk about "Drupal Databases: The Next Generation", which gave me a good insight into the current state of the Drupal database layer and how they plan to overhaul it for Drupal 7. The key points that I took away:

• A new API based on PDO
• Object-oriented, requiring PHP5
• Support for using prepared statements
• A unified access API
• A query builder
• More support for other database systems (currently Drupal supports MySQL and PostgreSQL only). In particular, they are …

It’s important that for any software application good standards exist. Standards ensure a number of key considerations. Standards are necessary to enforce and provide reproducible software and to provide a level of quality in a team environment, ease of readability and consistency.

If you were going to create a MySQL Naming Standard you have to make a number of key decisions. Generally there is no true right or wrong, however my goals tend towards readability and simplicity. In 2 decades of database design I’ve actually changed my preference between some of these points.

1. Pluralism

Option 1
All database objects are defined in the logical form, that being singular.

For example: box, customer, person, category, user, order, order_line product, post, post_category

Option 2

For database tables & views, objects are defined in plural. …

I was surprised to find yesterday when using MySQL 5.1.26-rc with a client I’m recommending 5.1 to, some information not seen in the EXPLAIN plan before while reviewing SQL Statements.

Using join buffer

+----+-------------+-------+--------+---------------+--------------+---------+------------------------+-------+----------------------------------------------+
| id | select_type | table | type   | possible_keys | key          | key_len | ref                    | rows  | Extra                                        |
+----+-------------+-------+--------+---------------+--------------+---------+------------------------+-------+----------------------------------------------+
|  1 | SIMPLE      | lr    | ALL    | NULL          | NULL         | NULL    | NULL                   |  1084 | Using where; Using temporary; Using filesort |
|  1 | SIMPLE      | ca    | ref    | update_check  | update_check | 4       | XXXXXXXXXXXXXXXXX      |     4 | Using …

I came across the OStatic Free hosting service that provide Solaris + Glassfish (Java Container) + MySQL.

They offer “Now you can get free Web hosting on Cloud Computing environment free of charge for up to 12 months. ”

The catch “accumulate 400 Points for participating on the site“.

A rather novel approach, you get 100 points for registering, but then only 5-15 points per task. The equates to approximately at least 30 tasks you need to perform, such as answering a question, or reviewing somebodies application. That seems like a lot of work?

In this case, Free has definitely a cost and time factor to consider.

We are always looking at different ways to help promote, inform and identify contributers, users and supports for Drizzle.

One way is to join the Linked In Drizzle group (click here when logged in). You will already see a few MySQL die hards, but also the need breed of names that are part of Drizzlemania.

For those that have been using Planet MySQL to follow the progress of Drizzle, we now have our own Planet Drizzle.

You can also get a RSS feed directly from http://feeds.feedburner.com/drizzle

I have been asked twice this week what version of MySQL I would choose for a new project.
As with most questions in life the answer is: It Depends?

In general I would now recommend for a new project to select 5.1, and he is why.

1. If it’s a new project and your not managing existing applications with older versions then 5.1 is slated for General Availability (GA) at some imminent time. Having been at Release Candidate (RC) for quite some time (almost 1 year), many people, both internally and in the community are just waiting for Sun/MySQL to get this version out.
2. MySQL 5.0 is in maintenance mode, it’s now 3 years old. MySQL is placing (I’m assuming) resourcing energies to current and future releases.
3. If your looking at releasing a product in the next 3 months for example, you do not want to consider the testing and deployment of a new version (e.g. 5.1) in the next 6-9 months.
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