I wrote:
> ... BTW, a quick grep for other calls of PageIndexTupleDelete suggests
> that SPGiST could make very good use of PageIndexTupleOverwrite, and
> there may be use for it in GIN too.
I've pushed this patch with some editorializing and some followup
work. The above remains as possible material for a future patch,
but I'm going to mark this commitfest entry as closed.
regards, tom lane