For the next week or more we will be in a *freeze* on HEAD, so please don't change any tables or add significant new code without directly contacting me first.
This lets us work on bugfixing and polishing 1.9 in HEAD where it's easier (less merging).
Soon we'll branch to MOODLE_19_STABLE however and you'll be able to do new stuff on HEAD again (a number of things are pending already).
In the meantime, I'm sure there are plenty of 1.9 bugs!