Yeah, looking back at my first reply I did get the order wrong: first the alter, then the empty noop. But once you run the alter and have a primary key (though the author clarified the table did have a PK already), I’d just use pt-osc to run the empty noop as that would basically do what the manual says.

Nice seeing you Evan! :)

Huh, if the table effectively already had a clustered index key (from the old PK) then I'm surprised that the auto_inc values would be assigned non-deterministically. I would have naively assumed that the values would be assigned in clustered index key order. Maybe this is one of those cases where too much logic is handled outside the storage engine?

Anyway yes nice to see you here too Fernando! Good call on the noop pt-osc, I always forget about all the cool tricks that tool can do when applied in non-obvious ways.