iostat is one of the most important tools for measuring disk performance, which of course is very relevant for database administrators, whether your chosen database is Postgres, MySQL, Oracle, or anything else that runs on GNU/Linux. Have you ever wondered where statistics like await (average wait for the request to complete) come from? If you look at the disk statistics the Linux kernel makes available through files such as /proc/diskstats, you won’t see await there. How does iostat compute await? For that matter, how does it compute the average queue size, service time, and utilization? This blog post will show you how that’s computed.

First, let’s look at the fields in /proc/diskstats. The order and location varies between kernels, but the following applies to 2.6 kernels. For reads and writes, the file contains the number of …

It may sound like a dramatic number, and that’s because it is. One thing that is enjoyable about working on beta applications is finding new solutions and better methods to improve the user experience. The original method for displaying the recent addition of overview analytics data in the beta version of Kontrollbase was to run [...]

One of the most widely discussed topics to go around the tech industry last year was the Oracle acquisition of Sun and what this meant for the MySQL database. This topic held up the merger with the US DOJ and currently has it stalled in the EU commission.

One of the primary forces behind these hold ups is a series of FUD articles written by Monty Widenius, the most recent just a few days ago. Monty has a huge following so whenever he writes up one of these articles it gets huge circulation and riles up the Slashdot and LAMP crowds.

I think that the open source community should be very skeptical about anything written by Monty on this topic, and should start looking at the big picture of what this merger means for themselves and the various players involved.

I don’t know why I haven’t been seeing many serious rebuttals to …

It’s New Year’s Eve, a date that should strike terror into the hearts of many, because tomorrow a bunch of their queries are going to fail.

Queries to “find all birthdays in the next week” and similar are always a nightmare to write. If you want to see a bunch of examples, go look at the user-contributed comments on the MySQL date and time function reference. This post is about a slightly saner way to do that. There’s still some nasty math involved, but a) a lot less of it, and b) at least the query will be able to use indexes[1].

So here’s my tip: instead of storing the user’s full birthdate, just store the month and day they were born. Try it. You’ll love it!

[1] Yes, I know Postgres can index a function. So this can be considered a jab at MySQL, which can’t.

Related posts:

1. …

If you’d like some improvements to the Cacti templates (MySQL, Apache, Memcached, and more) I’ve been maintaining, please make your voice heard — either write to the mailing list, or post a new issue (or comment on an existing one) on the issue list. I’ve got a bunch of work underway, including a test suite for ss_get_by_ssh.php.

Related posts:

1. Version 1.1.6 of Better Cacti Templates released I’ve
2. Version 1.1.2 of improved Cacti templates released I’ve
3. …

MySQL has a couple of sanity-check features to help keep you from doing dumb things.

• max_join_size is a configuration option for the mysqld server program. It throws an error if you write a query that the optimizer estimates will examine more than this number of rows.
• –safe-updates is a command-line option to the mysql client program. It throws an error if you write an UPDATE or DELETE without a) a WHERE clause that refers to an indexed column or b) a LIMIT clause. It also sets the max_join_size and select_limit variables.

The –safe-updates mysql client option actually sets three variables server-side. Let’s see the effects. First, the defaults:

Numeric types in MySQL have two varieties: - “precise” types such as INTEGER and DECIMAL; - the IEEE-standard floating point types FLOAT and DOUBLE. As a rule of thumb, the first group are for exact, “counted” quantities. The INTEGER types represent whole numbers, and DECIMAL represents “fixed point” decimal, with a preset number of places after the decimal point. Various widths of INTEGER are available in MySQL, from 8-bit TINYINT to 64-bit BIGINT. Calculations with integer types are fast, as they usually correspond to hardware register sizes. DECIMAL is commonly used for quantities like decimal currency where the number of digits of precision is known and fixed. For example, exactly counting pennies in two decimal digits. Computation with DECIMAL is slower than other types, but this is unlikely to impact most applications. In the other category are FLOAT and DOUBLE, which are the 32 and 64-bit IEEE standard types, which are usually …

I’m on the MySQL conference committee again this year, so I’ll be reading and voting on your session proposals. My past experience is that reading 400 session proposals is a mind-numbing job, and I will be optimizing it to save my time. That means I will be scanning your proposals and deciding very quickly how to vote. I wrote before about how to submit a great proposal, but I’ve refined my opinion since then. Here are my suggestions:

• Write for two audiences: reviewers and attendees. Both of us want the same thing: to decide as quickly as possible whether your session will be good.
• Write a strong title/headline. Don’t know how? …

The MySQL conference site for 2010 is live, and ready for your proposals. Submit! Submit! Submit!

Related posts:

1. There will be an O’Reilly MySQL Conference in April 2010 O’Re
2. How to write a good MySQL conference proposal I’m
3. Attending the IT Management Conference I’ll

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One of MySQL’s notable projects was splitting the product into two editions: Enterprise Edition and Community Edition. This move alienated many in the community, and failed to create meaningful differentiation on either side, even with a team of people beating the community bushes for “contributions.” The net differentiation was ultimately Jeremy Cole’s SHOW PROFILES functionality, which made Community better than Enterprise. Sun put less effort into making this split work, and eventually they abandoned it.

But that could change under Oracle’s stewardship. Oracle’s promises to maintain a GPL …