| From: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
|---|---|
| To: | Alexander Lakhin <exclusion(at)gmail(dot)com> |
| Cc: | Daniel Gustafsson <daniel(at)yesql(dot)se>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Mikhail Gribkov <youzhick(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Greg Nancarrow <gregn4422(at)gmail(dot)com>, Ivan Panchenko <wao(at)mail(dot)ru>, Teodor Sigaev <teodor(at)sigaev(dot)ru>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Subject: | Re: On login trigger: take three |
| Date: | 2024-02-05 20:28:24 |
| Message-ID: | CAPpHfdsb=1tMc85vBFMSOBojhfrah96_QsEH0-NuBrgKoDRDyA@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hi, Alexander!
On Mon, Feb 5, 2024 at 7:00 PM Alexander Lakhin <exclusion(at)gmail(dot)com> wrote:
> 05.02.2024 02:51, Alexander Korotkov wrote:
>
> > Usage of heap_inplace_update() seems appropriate for me here. It
> > avoids trouble with both TOAST and row-level locks. Alexander, could
> > you please recheck this fixes the problem.
>
> I've re-tested the last problematic scenario and can confirm that the fix
> works for it (though it still doesn't prevent the autovacuum issue (with
> 4b885d01 reverted)), but using heap_inplace_update() was considered risky
> in a recent discussion:
> https://www.postgresql.org/message-id/1596629.1698435146%40sss.pgh.pa.us
> So maybe it's worth to postpone such a fix till that discussion is
> finished or to look for another approach...
Thank you for pointing this out. I don't think there is a particular
problem with this use case for the following reasons.
1) Race conditions over pg_database.dathasloginevt are protected with lock tag.
2) Unsetting pg_database.dathasloginevt of old tuple version shouldn't
cause a problem. The next tuple version will be updated by further
connections.
However, I agree that it's better to wait for the discussion you've
pointed out before introducing another use case of
heap_inplace_update().
------
Regards,
Alexander Korotkov
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