I'd been doing some stress testing of my mysql application today, and I was hitting some weird cases. Several transactions were deadlocking - this was expected - but the number of records that got inserted into my table was more than the number that I expected after subtracting errors.

My test was fairly simple:

1. Fork 15 processes
2. Insert and update 100 records in each process, running each INSERT/UPDATE pair inside one transaction
3. ROLLBACK on error

Either the INSERT or the UPDATE was expected to fail due to deadlock, and the whole transaction should have rolled back leaving no record in the table.

Before I go on, I should mention that I was using InnoDB, which does support transactions.

What I expected was that the total number of records in the table + the total number of INSERT/UPDATE aborts due to deadlock should be equal to 1500 (15*100). What …

Theo Schlossnagle wrote a brilliant summary of one of the biggest challenges we discussed at the Velocity Summit in January:

What is this Velocity Summit thing? It was a bunch of web architects from highly trafficked sites sitting around talkin' smack. It was operated in Foo style. However, one thing that made me really appreciate this meet-up was the lack of self-importance displayed by attendees. Everyone was just there to talk -- not to make people understand how much they knew. We were talking about The O'Reilly Velocity Web Performance and Operations Conference: what it should be and why.

Two things that I walked away with were (1) a realization of the lack of a career path for people who do what …

I’m heading out to PostgreSQL Conference East in a few hours. Alas, I missed the first day but I’ll be there all day tomorrow. I hope to learn, meet people, and generally participate in goodness.

And no, I’m not an expert in PostgreSQL as I am in MySQL, but I have always held it in very high esteem. I am not going to try to spread the MySQL-ness into the PostgreSQL camp :-)

See you there.

mysql, PostgreSQL

Just a quick note to let folks know that today I coded up functionality to allow MySQL Forge users to re-vote on something they have already voted on. To re-vote, simply navigate to an item you've previously voted on, and click on the number of stars you wish to change your vote to. All done.

Also, I have corrected the ranking of items in display lists to take into account the number of votes an item has received (you're welcome, Giuseppe.). So, if both Project A and Project B have an average rating of 4 stars, but Project B has ten more votes than Project A, Project B will rank higher than Project A in the display lists.

So, get on to the Forge and start voting for your favourite projects, code …

Hopefully you are attending the MySQL Users Conference and are going to take advantage of the very deeply discounted exam prices. Normally the exams are $200 but we offer them at the UC for $25.

There will be two sessions each day of the three day conference. The session are at 10:30 and 13:40 for ninety minutes. And there is a special Exam Q&A Session will be held in the Magnolia Room, Tuesday from 1:00 pm - 1:30 pm.

We will be offering the Developer I & II, DBA I & II exams, and the Cluster exam. Please remember the Cluster exams is for those who already have the DBA certification.

The website omits mention of the Associate Exam but we will be offering that one also.

All exams will be administered in the Magnolia Room on the lobby level of the Hyatt Regency Santa Clara (adjacent to the …

 Properties:

Description:

This variable determines how many interrupted connections can occur from a host. If the number of interrupted connections from this host surpasses this number, that host is blocked from further connections. All of the …

A year ago, I criticized the under-development Falcon storage engine in MySQL 6.0 of failing to meet the demand of large-scale deployments. Falcon has now reached a beta phase and is included in the MySQL 6.0 alpha versions, most recent release of which is 6.0.4 this February. We're thinking of making an early test of Falcon in place of MyISAM/InnoDB for Habbo to see what to expect later on, so I reviewed the documentation again, and thought to look at my concerns from a year ago.

Falcon now supports multiple tablespaces per database, although the corresponding manual page still begins with the unfortunately misleading sentence of "all data ... is stored within a single file", and goes on to correct itself in the second …

This week’s Open Source Business Conference was a strange meeting of Enterprise IT users, venture capitalists, and free software entrepreneurs. The opening keynote was delivered by Red Hat’s freshly minted CEO Jim Whitehurst who gave a very modest speech noting that while Red Hat has been a leading open source company they have not necessarily been an open source leader. Whitehurst’s presentation lacked anything especially insightful or noteworthy and he has the advantage of being the new guy so he’s off the hook for anything that might have happened before he took the job.

What is apparent Red Hat’s no longer exciting. They’ve crossed over to …

As posted here I started to think about possible ways to implement database sharding/partitioning.

I finally found the time to start prototyping a MySQL Proxy based solution that would allow you to analyze and rewrite queries to direct them to different databases. So this would going to be a nearly 100% transparent solution (some queries are impossible to support due to the nature of having multiple tables in different locations).

How does it work?
The main goal is to split up mysql tables and optionally put each of the resulting partitions on different mysql servers.

For now I concentrate on splitting up big tables into smaller ones within the same database. Distribution of these tables (i.e. partitions) over multiple databases would be the final goal and a lot more challenging task (think of …