On Mon, Feb 14, 2022 at 2:19 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> No, at least not unless you plan to reimplement much of the WAL
> mechanism. You do need at least an LSN in the right place.
> I kinda doubt that you can get away with ignoring checksumming,
> either. On the whole, I think you'd be best off to use a standard
> page header; the amount you're saving by avoiding that will be
> minuscule, and the amount of work you cause for yourself probably
> not so much.
It isn't actually necessary for an index AM to use the standard
slotted page format to get the benefits that you mention, of course --
whether or not an index AM that uses standard page headers *also* uses
slotted pages with standard line pointers is a separate question. For
example, GIN posting tree pages don't use standard line pointers, but
still have a standard page header (and a generic GIN special area in
the opaque space).
I agree that it's hard to imagine that opting out of using the
standard page header format could ever make much sense. Principally
because the restrictions imposed on an index AM that uses the standard
page header format are very minimal, while the benefits are
substantial.
--
Peter Geoghegan