Michael, I was looking at your changes to speed up the insert path when a page write generation number changes underfoot, and I think we can do a similar test in the case of updating an existing key/value pair.

Basically, if we're the first update on an update list, or the transaction isn't a snapshot transaction, there's no reason we can't proceed even if the page's write generation number has changed, in other words, there are cases where there is either no update on the list or we don't care what updates are on the list, and the test is cheap enough to do in the serialized function.

If you agree, here's the change.