The latest from the MySQL community

The 2008 MySQL Conference & Expo registration is opened!

Time flies. We’re already at our sixth Users Conference! Looking at the announcement:

Co-presented by MySQL AB and O’Reilly Media, the conference will take place April 14-17, 2008, in Santa Clara, California. The event is expected to bring together over 1,600 open source and database users from some of the most exciting and fastest-growing companies in the world, as well as from the large and active MySQL Community. The program for 2008 will include keynote presentations by Jacek Becla of Stanford Linear Accelerator and MySQL CEO Marten Mickos.

Jay Pipes, our Program Chair, has lead a huge effort in identifying the best out of the near-300 proposals for sessions. …

A common question you hear from proprietary vendors when dismissing open source alternatives is “how many customers actually want access to the code anyway?” It is a question I put to an open source software vendor myself earlier this week while playing devil’s advocate.

The response - that the right to modify the source code is more important than actually doing it - is well known, but it is worth repeating in the light of recent events surrounding the Mindquarry open source collaboration project.

“It is strategically important for the customer that the source code is available, even if they don’t want to modify it,” was the response from the open source vendor I was talking to. There are a number of reasons for this:

• Open source adopters understand that it the open source model creates, at least in theory, a contestable model for support and services, freeing them from lock-in.
• They also …

In MySQL 4.1 and above the longest part of recovery after crash for Innodb tables could be UNDO stage - it was happening in foreground and was basically unbound - if you have large enough transaction which needed to be undone this could take long hours.
REDO stage on other hand always could be regulated by size of your Innodb log files so you could have it as large as you like. Read more about it here.

Since MySQL 5.0 the UNDO stage is running in background so it still can be the longest but would not keep server completely unusable (some limitations still apply though).

In the case I've been working on recently none of these parts was the longest one.
The server had about 65000 tables using innodb_file_per_table so "InnoDB: Reading tablespace information from the .ibd …

mysql_connect() function in PHP's MySQL interface (which for reference maps to mysql_real_connect() function in MySQL C API) has a $client_flags parameter since PHP 4.3.0. This parameter is barely known and almost always overlooked but in some cases it could provide a nice boost to your application.

There's a number of different flags that can be used. We're interested in a specific one, MYSQL_CLIENT_COMPRESS. This flag tells the client application to enable compression in the network protocol when talking to mysqld. It reduces network traffic but at the cost of some CPU time: server has to compress the data and client has to decompress it. So there's little sense in using it if your Web application is on the same host as the database.

When the database is on a dedicated server then compression essentially means trading CPU time (on both server and client) for network time. …

Until now PBXT has been ACId (with a lower-case d). This is soon to change as I have had some weeks to work on a fully durable version of the transactional engine (http://www.primebase.com/xt).

My first concern in making PBXT fully durable was to what extent I would have to abandon the original "write-once" design. While there are a number of ways to implement durability, the only method used by databases (as far as I know) is the write-ahead log.

The obvious advantage of this method is that all changes can be flushed at once. However, this requires that all data be written twice: once to the log and after that, to the database itself.

My solution to this problem is a compromise, but I think it is a good one. In a nutshell: short records are written twice, and long records are written once. When it comes to durability, this compromise, I …

So recently I found myself making a critical assumption that was incorrect and thought I would share in hopes that other people don't make the same mistake I did. I had helped a customer (who shall remain nameless) setup multi-master replication as a means for fail-over. Well, their network configuration changed such that one of the servers could not connect to the other. It was an easy enough fix. All I needed to do was to stop the slave, run CHANGE MASTER TO MASTER_HOST='192.168.1.123';, and start it back up right?

Wrong! Though the damage had already been done, I consulted the MySQL documentation which mentions that if you change the host of the master in this way, it assumes that the binary log file and position are no longer valid. Instead of throwing an error, it sets the master log file to '' and the position to 4. I'm …

So recently I found myself making a critical assumption that was incorrect and thought I would share in hopes that other people don't make the same mistake I did. I had helped a customer (who shall remain nameless) setup multi-master replication as a means for fail-over. Well, their network configuration changed such that one of the servers could not connect to the other. It was an easy enough fix. All I needed to do was to stop the slave, run CHANGE MASTER TO MASTER_HOST='192.168.1.123';, and start it back up right?

Wrong! Though the damage had already been done, I consulted the MySQL documentation which mentions that if you change the host of the master in this way, it assumes that the binary log file and position are no longer valid. Instead of throwing an error, it sets the master log file to '' and the position to 4. I'm …

As we head into the new year and to the next phase of development of the opentaps open source ERP and CRM system, there are several enhancements to the framework behind opentaps which we will be making. As you can see from this list, some of these enhancements will help make opentaps easier to use and to deploy, while others should open up new areas of possibility for our users:

New Forms and Document Management Tools

We plan on replacing xsl:fo with Jasper reports and iReport during the next year so that our users could easily customize all the forms and documents that their company needs, including orders, invoices, and receipts. We also hope to introduce a way for users to manage all these documents so that they no longer have to edit XML files.

Integrating Business Intelligence

We hope to integrate the new business intelligence tools in opentaps more deeply into the applications, rather …

I stumbled across this article today, which goes a long way toward explaining Oracle's affection for Linux. I fault Oracle for the way it went about embracing Linux, but I don't fault its financial acumen:

Last quarter, [Oracle] pointed out that its database market share actually tends to ...

Well, it’s that time of the year once more. The time when someone starts planning for the Users Conference, having received an acceptance notice of a session proposal. This year it came earlier than usual, because the CfP was started one month earlier, and thus we have a list of tutorials ready before Christmas.

So, let me do some advertising.
I am going to co-present a full day tutorial with Jan Kneschke. MySQL Proxy, the complete tutorial which will cover all about MySQL Proxy, and it will guide users to the creation of Lua scripts. When I proposed it, Jay asked me and Jan if we have enough material to cover 6 hours. After having been in three presentations on this subject, I’d rather ask myself if I can manage to cover all we know (and all that Jan’s volcanic production is …