>> No, that's not what I'm suggesting. My thought was that any V3 page
>> would be treated as if it were completely full, with the exception of
>> a completely empty page which can be reinitialized as a V4 page. So
>> you would never add any tuples to a V3 page, but you would need to
>> update xmax, hint bits, etc. Eventually when all the tuples were dead
>> you could reuse the page.
>
> But there's no guarantee that will ever happen. Heikki claimed you would need
> a mechanism to convert the page some day and you said you proposed a system
> where that wasn't true.
What's the scenario you're concerned about? An old snapshot that
never goes away?
Can we lock the old and new pages, move the tuple to a V4 page, and
update index entries without changing xmin/xmax?
...Robert