If someone can get me "junk" ( DB dump or a traffic generator) to fill my local phpBB forum so that it becomes properly/enough filled I can do benchmark tests to see how much difference I can make by adding foreign keys.
The main reason here is the clams of lack of speed of the queries to apply the idea topic I mentioned.
Anyway, It only works for when there are JOIN's, otherwise, it's just another hassle for the DB