From: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Dmitry Koval <d(dot)koval(at)postgrespro(dot)ru>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, andrewbille(at)gmail(dot)com, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org> |
Subject: | Re: BUG #17385: "RESET transaction_isolation" inside serializable transaction causes Assert at the transaction end |
Date: | 2022-03-09 23:36:35 |
Message-ID: | CAD21AoAEHLAJ3=_zoCicyaPSf9-2PnJBb8HixLwPN-rLA6wzNQ@mail.gmail.com |
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On Thu, Mar 10, 2022 at 12:11 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> writes:
> > On Wed, Feb 16, 2022 at 1:55 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> Yeah, I was considering that too. A new GUC_NO_RESET flag would be
> >> cheaper than running the check hooks during RESET, and probably
> >> safer too. On the other hand, we would lose the property that
> >> you can reset these settings as long as you've not yet taken a
> >> snapshot. I wonder whether there is any code out there that
> >> depends on that ...
>
> > Indeed. I guess that it's relatively common that the transaction
> > isolation level is set after BEGIN TRANSACTION but I've not heard that
> > it's reset after BEGIN TRANSACTION with setting non-default
> > transaction isolation level.
>
> Yes, we certainly have to preserve the SET case, but using RESET
> in that way seems like it'd be pretty weird coding. I'd have no
> hesitation about banning it in a HEAD-only change. I'm slightly
> more nervous about doing so in a back-patched bug fix. On the
> other hand, starting to call check hooks in a context that did
> not use them before is also scary to back-patch.
Agreed.
For back branches, it might be less scary to call check hooks for only
limited GUCs such as transaction_isolation.
> Do you want to draft up a patch that fixes this with a new
> GUC flag?
Yes, I'll update the patch accordingly.
Regards,
--
Masahiko Sawada
EDB: https://www.enterprisedb.com/
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