| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | 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>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, 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: | 2021-06-11 02:38:16 |
| Message-ID: | 20210611023816.fpc7v2wi3tclrsbh@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2021-06-10 19:15:59 -0700, Peter Geoghegan wrote:
> On Thu, Jun 10, 2021 at 7:00 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > I'm not convinced - right now we don't exercise this path in tests at
> > all. More assertions won't change that - stuff that can be triggered in
> > production-ish loads doesn't help during development. I do think that
> > that makes it far too easy to have state management bugs (e.g. a wrong
> > pincount in retry cases or such).
>
> The code in lazy_scan_prune() led to our detecting this bug (albeit in
> a fairly nasty way). The problematic VACUUM operations never actually
> exercised the goto as originally designed, for the purpose it was
> intended for. Perhaps we should add test coverage for the intended
> behavior too, but that doesn't seem particularly relevant right now.
Well, I'd like to add assertions ensuring the retry path is only entered
when correct - but I feel hesitant about doing so when I can't exercise
that path reliably in at least some of the situations.
Greetings,
Andres Freund
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