Right!
If you did, you’d not be asking. 
The likelihood that you’ll end up with a corrupt database is pretty high. And then no one will be able to help you.
Dump your database and restore on your local Discourse server (or anywhere that it can connect to–I’ve done larger imports with a remote database over my home internet connection) and then run the existing script.
It’ll be much easier to use Ruby that you don’t understand than to understand it well enough to figure out how to write the SQL. I learned Ruby a long time after I wrote my first importer.