On Tue, Dec 17, 2024 at 10:51 AM Robert Haas <robertmh...@gmail.com> wrote: > I think this amounts to inventing a new way to mark a tuple as dead, > but I don't think we need to do that. We could just mark the line > pointer LP_DEAD without actually touching the space that contains the > tuple. At least, I think that would work.
You might well be right about that. HOT chains might make things more complicated (a heap-only tuple can only be set LP_UNUSED), but we could probably figure that out if we had to. I'm not entirely sure that this would be worth the effort. I believe that having to wait for a cleanup lock is rare in general. On the other hand, it'd be convenient if the high-level design of VACUUM/autovacuum scheduling could freely ignore the possibility of having to wait for a cleanup lock. > The only question in my mind > is whether whatever we propose to do here would violate the locking > rules documented in src/backend/storage/buffer/README. In my opinion, > those rules are a bit vaguely worded in some places, but I interpret > #1 and #2 as meaning that you can't look at the line pointer array > without some kind of content lock, so an exclusive content lock should > be good enough to mark a line pointer dead as long as you don't > relocate any tuples. That is also my interpretation. -- Peter Geoghegan
