I recently upgraded from Kubuntu 13.10 to 14.04. It generally went smoothly. I only had an issue with Thunderbird crashing into bug 985986 and then Quassel starting up extremely slowly like 4-6 minutes until I can see and send messages.
I’ve been using Quassel for years and my database (sqlite) had grown to 750M. Since I was told on #quassel that sqlite doesn’t perform well with that big databases I assumed that was it. I made a copy of my database and deleted older messages (in backlog table) from one and newer ones from another. This way I have an archive if I want some information out of it but it isn’t available as scrollback all the time when I don’t need it. I then tried using Quassel again with a database less than 300M. It was still slow (around 30s) to startup.
Today I tried downgrading quassel from 0.10.0 to 0.9.1 that I used in 13.10. That did not help, Quassel remained slow. I then tried downgrading sqlite3 (libsqlite3-0 and sqlite3 packages) from 3.8.2 to 3.7.17. That sped up Quassel to normal few seconds it takes to fetch messages from ZNC. I then upgraded Quassel to 0.10 again and it remained fast. I also tried upgrading sqlite to Utopic packages with 3.8.5 but that was slow as well.
So it seems that for the queries Quassel executes on startup (of which I have no idea what they are) there’s been a regression in sqlite3 between versions 3.7.17 and 3.8.2. Using sqlite3 from Saucy works as a workaround.