| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: pg14b1 stuck in lazy_scan_prune/heap_page_prune of pg_statistic |
| Date: | 2021-07-16 23:13:03 |
| Message-ID: | CAH2-WznAOqF2HfmF_RdqTATfDwV=kFtKxaMbC8HqvPsZ_wW4cQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Jun 16, 2021 at 1:21 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> Oh yeah, I think that I get it now. Tell me if this sounds right to you:
>
> It's not so much that HeapTupleSatisfiesVacuum() "disagrees" with
> heap_prune_satisfies_vacuum() in a way that actually matters to
> VACUUM. While there does seem to be a fairly mundane bug in
> GetOldestNonRemovableTransactionId() that really is a matter of
> disagreement between the two functions, the fundamental issue is
> deeper than that. The fundamental issue is that it's not okay to
> assume that the XID horizon won't go backwards. This probably matters
> for lots of reasons. The most obvious reason is that in theory it
> could cause lazy_scan_prune() to get stuck in about the same way as
> Justin reported, with the GetOldestNonRemovableTransactionId() bug.
Any update on this, Andres?
--
Peter Geoghegan
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