| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Greg Stark <stark(at)mit(dot)edu> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Subject: | Re: Removing more vacuumlazy.c special cases, relfrozenxid optimizations |
| Date: | 2022-02-05 04:20:50 |
| Message-ID: | CAH2-Wz===BNgQih0hEgJTHBOzmYASvdDGZfsYRXS2q8LoLqVaw@mail.gmail.com |
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On Fri, Feb 4, 2022 at 10:44 PM Peter Geoghegan <pg(at)bowt(dot)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
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