On Tue, Jun 11, 2019 at 8:59 AM Robert Haas <robertmhaas@gmail.com> wrote:
> I don't think that including visibility information in indexes is a
> bad idea; we've thought about making zheap do this someday. But I
> think that we need to use some more sophisticated approach involving,
> maybe, undo pointers, or some other kind of magic, rather than just
> widening the tuples. I expect that just widening the tuples would be
> good enough to win for some use cases, but I think there would be
> others that lose heavily.
+1. Limited visibility information would make sense (e.g. maybe a per
tuple all-visible bit), which would have to be backed by something
like UNDO, but storing XIDs in tuples seems like a very bad idea. The
idea that something like this would have to be usable by any possible
table access method seems unworkable in general.
Sometimes it seems like the table access method work could use some
specific non-goals. Perhaps I just haven't being paying enough
attention to have noticed them.
--
Peter Geoghegan