Sometimes it´s useful to take a look at the querylog, when you see a growing graph in a monitoring tool and think "what´s happening there?"
But there is no need to keep it always enabled as it produces I/O load.
To enable the querylog, the mysqld must be restartet, which means downtime and this is not acceptable. So I found the following way:

• start the mysqld with querylog enabled
• delete the querylog file and keep the mysqld running
• issue a "flush logs" when you need the querylog. The mysqld re-creates the file and you can look at it.
• remove the querylog file when finished

Ok, not the perfect way, but it seems to work. But don´t forget the side effects of a "flush logs". This command creates a new binlog and errorlog too.

It’s been a long time since I bought a book about mysql, so I thought I would ask what were some of the recent good books around about mysql.

The only good book I know is ‘high performance mysql’, but it is from 2004. so I’m concerned it’s a bit dated.

So.. what’s on your bookshelves?

In the mid-90s, at the very starting edge of the dotcom boom, I was the lead tech guy behind a project, we put a nationwide yellow pages database on the web, ypol.com.

At the time, nobody else had done it, but we were sure that many other people had had the same idea. And since it's rare for someone to care about finding a plumber or locksmith in another state in the middle of the night, of course I had location based searches from the start.

It was, in fact, my first real encounter with using Oracle, Sybase, and using Perl to interface to a DB. (This was before Perl5, so there was no DBI module, so it was all oraperl.)


It looks like someone has actually patented the idea of location based searches on a online yellow pages database, has put together an investor-based lawsuit machine, and has fired the first salvo by suing Verizon.

I'm pretty damn sure my old YPOL project is prior …

Yesterday I was asked for help concerning a replication problem with one of our test systems. My colleague had already installed a fresh dump he had created with mysqldump ... --master-data. The dump looked ok and contained a master configuration statement:

...
CHANGE MASTER TO MASTER_LOG_FILE='master-bin.000127',MASTER_LOG_POS=4462223;
...

The slave was provided with the correct user, password and host name for this master. Nevertheless issuing a START SLAVE did not work. In the slave .err file we found this:

 
...
050327 20:54:51 [ERROR] Error reading packet from server: Client requested master to start replication from impossible position (server_errno=1236)
050327 20:54:51 [ERROR] Got fatal error 1236: 'Client requested master to start replication from impossible position' from master when reading data from binary log
...

After some fiddling around and searching the net for …

Yesterday I was asked for help concerning a replication problem with one of our test systems. My colleague had already installed a fresh dump he had created with mysqldump ... --master-data. The dump looked ok and contained a master configuration statement:

...
CHANGE MASTER TO MASTER_LOG_FILE='master-bin.000127',MASTER_LOG_POS=4462223;
...

The slave was provided with the correct user, password and host name for this master. Nevertheless issuing a START SLAVE did not work. In the slave .err file we found this:

 
...
050327 20:54:51 [ERROR] Error reading packet from server: Client requested master to start replication from impossible position (server_errno=1236)
050327 20:54:51 [ERROR] Got fatal error 1236: 'Client requested master to start replication from impossible position' from master when reading data from binary log
...

After some fiddling around and searching the net for …

MySQL Connector/Net 5.1.2 a new version of the all-managed .NET driver for MySQL has been released.

Connector/Net 5.1 represents a change in how we package our products. Until now, we've shipped our core provider and the Visual Studio integration bits as separate downloads. This has become a bit of a problem. Often we would fix a bug that involved changing code both in the VS package and in the core provider. This provided a versioning problem where users would need to upgrade both products to see the benefit of the bug fix. To solve this, we've decided to discontinue Tools for Visual Studio as a separate product and have, instead, integrated it into a new Connector/Net installer. We hope this provides a better "out of box" experience for our users.

All previous versions of Tools for Visual Studio should be uninstalled prior to installing this product.

Version 5.1.2 works with all versions of MySQL …

OverviewTest suites are hard, but your business needs to have one.
They are hard because modern applications are complex.
Technology can help you. There are tools that can simplify the task of creating a thorough test suite.

Does your main business have a regression test?The likely answers to the above questions are:

• Yes. - Good chap. Keep up the good work. You may stop reading, but just out of curiosity, read on.
  
• No. I don't need one. - You may stop reading. Most likely your business is already doomed. :)
• No. I don't have time (don't know how) to make one. - Keep reading. There is something for you.

What's a regression test? Is a useful watchdog that tells you if your software is working the way it was intended to.
If you don't have one, you have no quick and reliable …

Wow! It has really been 4 months since my last post?? Moving over to development has cut into the time I had for blogging, documenting, communicating, you name it! We are coding like crazy.

Well, I'm back because I am heading out to ODTUG Kaleidoscope next week, and in preparation for the show, I decided to setup Pentaho on Oracle's Java Edition App Server, which is OC4J, which is based on the Orion app server. I was pleased that I managed the migration in less than a day, and I wanted to share the steps with all those folks who are too impatient to wait for this to get into our J2EE deployment distribution :)

Mind you, it takes a bit of tweaking, but it is certainly very do-able, and all server features are stable (minus the portal stuff, I didn't get a chance to address moving the portal over). Here is the repro of where I started, what I …

Today, Lenz was putting together some stats on PlanetMySQL feeds added since January this year, and asked in an email whether he should include totals in the stats. I responded yes, and offered a quick SQL solution to get those numbers out of the database. I thought it might be useful for others, so here goes...

Rolling sums (or averages) are a way to include a running, or rolling, aggregate of certain columns in the output of your SQL. For instance, let's say you want to list order totals, grouped by product category, but in each row of the final output, you wish to include the running total of all rows in the output up to and including the current row. A running sum would allow you to do such a calculation.

In the specific example that came up today, Lenz had the following SQL statement which listed the month the feed was …

By Tim O'Reilly

This story has been heard before: distribute millions of copies of your open source software for free, then build a business by servicing the customers who're using that software. Red Hat, JBoss, MySQL have all made a great success with this business model.

Why did it take so long for someone to figure out that this could also be a brilliant new take on the online advertising business? Step one: distribute a free, open source ad server; step two: package up the resulting publisher network for advertisers, regardless of which ad network they want to work with; step three: build additional services for those advertisers.

I caught up last week with Scott Switzer, OpenAds co-founder and community activist, to learn a bit more about OpenAds. It took me a few minutes to understand the OpenAds story (and even now, I may have a few details wrong.) As it turns …