As a heads-up for anyone using postgresql 9.1 or later (9.0 is the only confirmed-correct version) anyone running a slave server, it appears that there’s an issue with the upgrade script which will result in an incorrect track table in most cases.
An ostensible fix that was previously mentioned here does not work. We’re still working on a fix and will update this post as we have more details.
There is a fix, see http://blog.musicbrainz.org/?p=1962 for instructions. Thanks for your patience!