One important bottleneck in the MySQL Server is the log_sys mutex in InnoDB. Experiments using mutex statistics showed that this mutex was accessed about 250k times per second and that about 75% of those accesses had to queue up to get the mutex. One particular nuisance is that while holding the log_sys mutex it is necessary to grab the buffer pool mutex to put the changed pages to the start of the flush list indicating it is now the youngest dirty page in the buffer pool (this happens as part of the mini commit functionality in InnoDB). To some extent this contention point is decreased by splitting out the buffer flush list from the buffer pool mutex.

We found a simple improvement of this particular problem. The simple solution is to introduce a new mutex, log_flush_order mutex, this mutex is acquired while still holding the log_sys mutex, as soon as it is acquired we can release the log_sys mutex. This gives us the property that the …

The MySQL team at Oracle has been very busy! Tomorrow, Sept. 19th, we welcome the MySQL users and community to Oracle OpenWorld - this will be a first. We all are very excited and have been working hard to make this worth your while.

Details on MySQL Sunday

Day and Date: Sunday, Sept. 19, 2010

Time: 12:30 pm onwards (registration is prior to 12:30 and will be at Moscone location)

Location: Marriott Marquis, San Francisco

Check out the MySQL Sunday agenda.

Don't miss the opening keynote by Edward Screven, closing keynote by Marten Mickos and sessions delivered by your favorite community presenters including Mark Callaghan, Sheeri Cabral, Ronald Bradford and many more.

 Hope to see you tomorrow! …

I pushed more changes to the Facebook patch for MySQL 5.1 -- revisions 3551 to 3564. Most of the patches are bug fixes for previous patches including code and test changes. This includes fixes for:

* InnoDB fast checksum - 3551, 3552

* group commit - 3555,   …

Today is all airports and flights. The flight between London and San Francisco is not too bad, but I don’t like long haul flights and for 12 hours I can sympathise with sardines and anchovies…

Tomorrow it will be different. The weather looks good, the sessions very interesting. Just few hours to settle, review the presentation and relax a bit before it begins. Then, Oracle Open World is going to open on Sunday evening at the Moscone Center.

What about MySQL?

Sunday is all MySQL! We will have opening keynotes from Edward Screven and the MySQL team. We will have technical sessions all afternoon and a closing keynote from Marten Mickos in the evening. The program for MySQL Sunday is here.

If you cannot participate in person, I am sure you will find presentations and videos soon after the event.

My …

ScaleDB and Oracle RAC are both clustered databases that use a shared-disk architecture. As I have mentioned previously, they both actually share data via a shared cache, so it might be more appropriate to call them shared-cache databases.

Whether it is called shared-disk or shared-cache, these databases must orchestrate the sharing of a single set of data amongst multiple nodes. This introduces two challenges: the physical sharing of the data and the logical sharing of the data.

Physical Sharing:
Raw storage is meant to work on a 1:1 basis with a single server. In order to share that data amongst multiple servers, you need either a Network File System (NFS), which shares whole files, or a Cluster File System (CFS), which shares data blocks.

Logical Sharing:
This is specific to …

The Drupal community just recently released another alpha test release of their upcoming Drupal 7 version, to shake out the remaining bugs and to encourage more users to test it.

If you would like to give it a try, but you don't have a free server handy, how about using a virtual machine instead? Using the fabolous SuSE Studio, I've created an appliance based on openSUSE 11.3, Drupal 7.0-alpha7 and MySQL 5.1 with the InnoDB plugin and strict mode enabled (both for the …

One of many things I really enjoyed working as a Sales Engineer back at MySQL Ab and Sun was that I was paid full time to encourage companies to use open source for their database layer. While Linux has already become the norm for the operating system on servers, and open source alternatives exist for app servers, it wasn't until a few years ago we really started seeing major traction of that in the database layer. And I was happy to be a small part of it!

I'm not really a salesy person. I mean I'm good at evangelizing something I believe in, addressing customer business needs and such. But you couldn't get me to lift a finger just to meet a quota, if I didn't really believe in the product. Which is what good sales guys can do. (Also known as "selling what you have in the truck".)

But thinking back at my time selling MySQL, I felt it was a great privilege to be paid a salary to travel to companies around Europe and spend a day …

Last night I was the invited guest at the SF MySQL Meetup. In my presentation “Successful MySQL Scalability” I talked about a set of principles to ensure appropriate system architecture, data availability and best practices to build an ideal solution for your business. The presentation was also live streamed and is available online.

Successful MySQL Scalability

We're proud to introduce the sqlexamples.org community, a resource for database developers and administrators. Our aim is it to improve the availability of free (as in free speech) SQL and NoSQL related database examples of all kinds. We're not just focused on MySQL. Related is for example:

• syntax examples
• database schemata
• database related source code
• <your idea here>

A lot of valuable database related content gets published day by day in countless blogs all over the web. Our aim is it to archive and index this knowledge in a central database, open and accessible for everyone. When you want to help us building such an useful archive, all you have to do is to submit your RSS feed to sqlexamples.org . Additionally, content can be published directly on our platform if you like.

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On DBA Survivor, Thomas LaRock blogged about “Finding a Good DBA“.  This is a reply.

I mostly agree what what LaRock said. Managers believe databases fall into the same category as email servers and domain name servers. System administrators are expected to take care of them all. And, having been a SysAdmin myself, I know as long as the thing is working they’re good.

I was also an application developer for a number of years as well. From that point of view, you are working as fast as you can while still trying to make your code run as fast as it can. You don’t have full access to the SQL servers. You might test a few different SQL queries to see witch is faster, but you can’t get access to the configuration files.  Asking the SysAdmin to change from RAID-5 to RAID-10 …