It might not work on PostgreSQL, even though it will talk to it. The syntax for making an autoincrementing column in the database seems to be different on all databases, and there's no code for doing it on PostegreSQL, so post numbers might not work right.
That said, what is the problem with the current SQL dump and Postegres? It should be simple enough to work with any SQL database, unless there is some lingering bug (there have been a number of them, so use the newest Wakaba to generate it).