GitHub is a special case, perhaps in all of computerdom, in that most of their public data is stored not in (SQL) databases, but in git repositories. That's ra

GitHub is a special case, perhaps in all of computerdom, in that most of their public data is stored not in (SQL) databases, but in git repositories. That's rather unique! So we know they must already have a great indexing and search system in place, and they can't use foreign key constraints on most of their data, anyway. Git simply doesn't have that. It's not that kind of database. Given this environment, it's not surprising they don't use FKs. It wouldn't surprise me if they don't use JOINs much! Throw it all in a repo, and let the indexer sort it out. That's great for them, but my data isn't shaped like that. Data types and referential integrity are more important to me than history and bisection.