The "default" is a 32 bit int, large enough for almost 4.3 billion records. That is enough for the vast majority of tables, and going to a 64 bit int has some p

The "default" is a 32 bit int, large enough for almost 4.3 billion records. That is enough for the vast majority of tables, and going to a 64 bit int has some performance implications, which at GitHubs scale is absolutely something they need to take into consideration, just as they should have with the table size.