That sounds like a pretty reasonable educated guess to me (that's meant positively, I'm just ops enough that I consider lots of things I hope I know to be in th

That sounds like a pretty reasonable educated guess to me (that's meant positively, I'm just ops enough that I consider lots of things I hope I know to be in that category). But it -does- still leave the question of how well the storage layer reports table statistics and how that interacts with the planner. If I sound suspicious, it's because I ran into a situation recently where a SELECT inside a transaction on mysql Aurora somehow (as far as I can tell, I was helping out at a couple removes so if you're reading this and it's relevant to you please don't believe me without testing yourself) took a whole table lock in a situation where I am pretty damn sure that for all its 'fun' actual InnoDB would've locked a page at most. So ops goes.