Actually, looking at get_attstatslot, I realize it was already designed to do that -- just pass zero for flags. So we could do it as attached.
Yes, it is. Using zero flag would short-cut get_attstatsslot() to just return whether the slot type exists without loading it. Do you think we need to emphasize this use case in the comments for 'flags'? It seems currently there is no such use case in the codes on HEAD.
I wonder whether we need to also check statistic_proc_security_check() when determining if MCVs exists in both sides.
