The first is that I always have to wonder what people mean when they say "gigantic". I've seen people say that about data sets from a few thousand lines to billions. Usually people mean something more like the former, which is a much easier question to answer than the latter.

The second is that if you're regularly faced with this kind of problem, you should get familiar with how to use databases. With a database you could give your columns real names, and the sorting and grouping functionality that you asked for is standard. (Along with many more complicated features.)