There is currently no way to connect to Google Search Appliance natively with Tableau.
Tracy Rodgers - thanks for your feedback - maybe there is a way? -
I've been doing a bit of research and discovered you can set up Google Analytics to report on a Google Search Appliance (see reference below). This should then allow you to use the Google Analytics Connector in Tableau.
Problem we now have is that we don't want to expose our GSA search results in a cloud service for legal reasons!
As I'm now unable to try this solution in practice I would be most interested if someone else could.