Daniel Schneller's Blog

Yesterday I read about the final release of Ubuntu 6.10, Edgy Eft. As for my good experiences with Dapper Drake I decided to upgrade. Having sort of a Debian history I was quite confident that a dist-upgrade would work quite flawlessly, especially since I had not made any deep modifications of my system (definitely a point for Ubuntu here! :)).PreparingI went to the Ubuntu homepage and read the Upgrade Notes. I had always wondered - however not really bothered to find out either - what this alternate install CD was. Now I know that it is used to save bandwidth in the upgrade process, because it can be used as a local repository source. I do however wonder, why this cannot be done with the regular install media. But anyways...UpgradingI ran the CD based upgrade as described in the upgrade notes. A graphical tool came up and asked me whether I wanted to download updates of more recent packages from the net. I said yes, suspecting that there would not be that many of them, as the whole …

Maybe I shouldn't do vacations anymore... This time I got a nasty flu two days after my return. Well, slowly I am feeling better and thought I might just tell you that the installation of the Flash Player 9 beta for Linux worked like a charm on my Ubuntu Dapper Drake (6.06) machine.I just downloaded the archive from Adobe Labs, uninstalled the previous version using apt-get and put the new libflashplayer.so file into my private plugin directory. Apart from the ds@yavin: ~$ sudo apt-get remove flashplugin-nonfree everything is described in the readme.txt file that comes included in the archive.It is really great to have synchronous audio/video playback for the first time under Linux. About time, but hey, thanks anyway :)

We are currently preparing a MySQL 4.1 to MySQL 5.0 migration. First tests showed a very nasty problem, however.One of our test cases incorporates queries against DECIMAL columns that use strings as the queried values. In MySQL 4.1 this works flawlessly. The reason behind this is that in contrast to 4.1 the newer server version does a (in my opinion very stupid) conversion from String to double, which in many cases cannot correctly store the precise value.This may lead to very subtle bugs, especially when using an optimistic locking approach as we do. We only noticed the problem, because we got a ConcurrentModificationException, as an update query that contained a string-ized BigDecimal did not match any rows.See MySQL bug reports 23260 and 22290 for more details.Right now this leaves us with little options but to not migrate to 4.1 as our application has several hundreds of thousands of lines where most of the database access is handled by an OR mapping layer, but there are also nume…

Today I spent several hours trying to find a problem in our application until I found out there was a problem on the MySQL side. In our setup we have several slave machines that replicate data from a master server. The slaves are configured with a series of replicate-do-table directives in the my.cnf file so that only parts of the schema get replicated. The remaining tables are modified locally, so to avoid conflicts they are not updated with data coming from the master.We do however have the need to replicate data from the master for some special-case tables. To solve this we usually have a column that indicates whether a record was created on a master or a slave machine and use an appropriate WHERE clause in all updates. This avoids collisions in concurrent INSERTs on the master and the slave. The application knows which of the two records to use.Due to historical reasons I do not want to elaborate on we did not use such a distinction column for one table (let's call it T1). Ins…