We have a table which essentially represents a shallow graph (rows in the table can have links to to one or more other rows in the table). It would probably be

We have a table which essentially represents a shallow graph (rows in the table can have links to to one or more other rows in the table). It would probably be interesting if we could define a distance metric in terms of those links: "find all rows reachable in 3 links from this starting row". This probably isn't ideally done by this sort of index, as it would be a pretty weird sort of distance metric, if it's even a valid one (most rows aren't connected, meaning the "distance" between most rows would be infinite, and our query would really be "WHERE distance < infinity"). But it's good to know there's some kind of support for it!