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Subject: Re: Should vacuum process config file reload more often
From: Daniel Gustafsson <daniel@yesql.se>
In-Reply-To: <CAAKRu_Z8+UqT8D=k-bVuE8525Z3ri4_xfCuOVnuQ-5yWc+tUew@mail.gmail.com>
Date: Thu, 27 Apr 2023 23:25:30 +0200
Cc: Masahiko Sawada <sawada.mshk@gmail.com>,
 John Naylor <john.naylor@enterprisedb.com>,
 Robert Haas <robertmhaas@gmail.com>,
 Andres Freund <andres@anarazel.de>,
 Tom Lane <tgl@sss.pgh.pa.us>,
 Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
 PostgreSQL Hackers <pgsql-hackers@postgresql.org>,
 Amit Kapila <amit.kapila16@gmail.com>
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To: Melanie Plageman <melanieplageman@gmail.com>
Archived-At: <https://www.postgresql.org/message-id/7A5D2190-5BF3-45F6-AE54-471D23C0CF1B%40yesql.se>
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> On 27 Apr 2023, at 16:53, Melanie Plageman <melanieplageman@gmail.com> =
wrote:
> On Thu, Apr 27, 2023 at 8:55=E2=80=AFAM Daniel Gustafsson =
<daniel@yesql.se> wrote:
>>=20
>>> On 27 Apr 2023, at 14:10, Masahiko Sawada <sawada.mshk@gmail.com> =
wrote:

>>> Good catch. I think the problem is that vacuum_rel() is called
>>> recursively and we don't reset VacuumFailsafeActive before vacuuming
>>> the toast table. I think we should reset it in heap_vacuum_rel()
>>> instead of Assert(). It's possible that we trigger the failsafe mode
>>> only for either one.Please find the attached patch.
>>=20
>> Agreed, that matches my research and testing, I have the same diff =
here and it
>> passes testing and works as intended.  This was briefly discussed in =
[0] and
>> slightly upthread from there but then missed.  I will do some more =
looking and
>> testing but I'm fairly sure this is the right fix, so unless I find =
something
>> else I will go ahead with this.
>>=20
>> xid_wraparound is a really nifty testing tool. Very cool.Makes sense =
to me too.
>=20
> Fix LGTM.

Thanks for review. I plan to push this in the morning.

> Though we previously set it to false before this series of patches,
> perhaps it is
> worth adding a comment about why VacuumFailsafeActive must be reset =
here
> even though we reset it before vacuuming each table?

Agreed.=20

--
Daniel Gustafsson