Minor Description
VTITemplate defines getMetaData() as an abstract method. That method doesn't appear to be needed for user-defined table functions, so it would be good to provide a default implementation (could just throw an exception) so that less boilerplate is needed when writing table functions. The method does however get used by system VTIs, which is probably why it was made abstract in the first place. The system VTIs should still override getMetaData().