Ivo-
I think the bottleneck is using a database mangement system (here mysql). So my question is: What is the advantage of using it? As I understand the toppic dbms is usefull for very structured redundant data.
This is an eternal debate. You may want to look at MoinMoin, which stores all its pages in plaintext and still manages to be very powerful:
Also see my review of several DB and non-DB based wiki engines in c't 25/03.
Using a database allows us to run a set of highly complex queries to examine the relationships between articles and the metadata about articles. In fact we can even examine the relationship between articles and users (watchlist), or between the metadata of different articles (redirect status in "What links here").
All that would only be possible using ugly hacks without a database -- you would effectively have to build your own mini-DB to store this metadata, and most text-based wikis do this. They get extremely slow when it comes to very basic stuff such as listing backlinks or doing a fulltext search. Not on a small wiki, but on one of the size of Wikipedia. I have imported large datasets into TWiki etc., and many operations became practically unusable.
The MediaWiki FT search has locking issues. It's very fast for a normal wiki, but for a huge one like Wikipedia it tends to get in a deadlock state. That's why we have to disable it on Wikipedia. Some other queries could also be made faster. Many of our queries have been optimized now and every single one should eventually return results with a response time of milliseconds.
It is a fallacy that a database makes things more complicated. It makes them much easier because you don't have to worry where to store something before implementing it. How do you want to store your user prefs, the redirect info, the recent changes table, the page history, always keeping quick access in mind? Usemod, Twiki etc. all use ugly hacks for that kind of stuff.
In short, a DB is faster, cleaner, and more convenient. We benefit from the thousands of man hours that the MySQL developers have invested in building a scalable, fast, powerful multi-user database instead of having to reinvent the wheel whenever we want to do something that goes beyond "show me that file".
Regards,
Erik