Filecache.path_hash? What/How is it hashed?

I’m writing a script to automatically tag files based on a known data source. I’m acting right on the database, because it’s more flexible.
I look up the file in ‘filecache’ by ‘name’, as they are controlled and named via an ID for another service, and by ‘storage’, then add the ‘systemtag’ if missing, and finally create the ‘systemtag_object_mapping’.
Unfortunately, the one issue I have is that the ‘’ column isn’t indexed. I figure I can use the already indexed path_hash column, but I don’t know how or on what data the path is hashed. Is it a simple md5 of the path column or what?