From the online documents: http://docs.graylog.org/en/2.4/pages/lookuptables.html
Data adapters are used to do the actual lookup for a value. They might read from a CSV file, connect to a database or execute HTTP requests to receive the lookup result.
The statement “connect to a database” lead me to believe there would be an option available for some type of Database/MySQL server. I would enter the server IP: Port, username, and password for a connection. insert some magical SQL select and I would be able to map some data.
My fallback is to occasionally export to CSV blah blah…