I've been trying that, and I just keep running into miserable query performance.

What order of magnitude do you use this on and find it acceptable? 1MB, 1GB, 1TB, 1PB? At 1GB it seems okay. At 10GB things aren't great, at 100 GB things are pretty grim, and at 1TB I have to denormalize the database or it's all broken (practically).

I'm not a database expert, but I don't feel like I'm asking hard questions, but I'm running into trouble with something I thought was 'easy', and matches what you're describing.