On Fri, Feb 4, 2022 at 10:44 PM Peter Geoghegan <pg@bowt.ie> wrote:
> Right - it's practically inevitable that you'll need an
> anti-wraparound VACUUM to advance relfrozenxid right now. Technically
> it's possible to advance relfrozenxid in any VACUUM, but in practice
> it just never happens on a large table. You only need to get unlucky
> with one heap page, either by failing to get a cleanup lock, or (more
> likely) by setting even one single page all-visible but not all-frozen
> just once (once in any VACUUM that takes place between anti-wraparound
> VACUUMs).
Minor correction: That's a slight exaggeration, since we won't skip
groups of all-visible pages that don't exceed SKIP_PAGES_THRESHOLD
blocks (32 blocks).
--
Peter Geoghegan
