My preference would be to create the database tables before trying to load the data, but it depends on how you want to do it. You can always start up postgresql from a command line, connect to the Metasploit database as the msf user, and see what tables are used. This info is in the /opt/framework/config/ database.yml file. I've never looked for the script Metasploit uses to create its database, but try doing a grep -r from /opt/framework. For the ultimate authority on the framework, the Metasploit mailing list is the place to go. HDM and other developers are often on there.