Re: vacuum verbose no longer reveals anything about pins

On Thu, Jun 30, 2022 at 5:57 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> I was dismayed to learn that VACUUM VERBOSE on a table no longer tells
> you anything about whether any pages were skipped due to pins.

VACUUM VERBOSE will show a dedicated line that reports on the number
of pages that we couldn't get a cleanup lock on, if and only if we
couldn't do useful work as a result. In practice this means pages that
had one or more fully DEAD tuples that couldn't be removed due to our
inability to prune. In my view this is strictly better than reporting
on the number of "skipped due to pins" pages.

In the case of any pages that we couldn't get a cleanup lock on that
didn't have any DEAD tuples (pages that are not reported on at all),
VACUUM hasn't missed any work whatsoever. It even does heap vacuuming,
which doesn't require a cleanup lock in either the first or the second
heap pass. What's the problem with not reporting on that?

--
Peter Geoghegan