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From: Sascha Kuhl <[email protected]>
To: Fujii Masao <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Kyotaro Horiguchi <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: sequences vs. synchronous replication
Date: Tue, 28 Dec 2021 09:28:30 +0100
Message-ID: <CAPvVvKDjqozx5szNTRthNiFePBvPT+Td0e8rqjb23oF8Py4e6A@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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Sequence validation by step, in total is great. If the sequence is Familie
or professional, does it make sense to a have a total validation by an
expert. I can only say true by chi square Networks, but would a medical
opinion be an improvement?

Fujii Masao <[email protected]> schrieb am Di., 28. Dez. 2021,
07:56:

>
>
> On 2021/12/24 19:40, Tomas Vondra wrote:
> > Maybe, but what would such workload look like? Based on the tests I did,
> such workload probably can't generate any WAL. The amount of WAL added by
> the change is tiny, the regression is caused by having to flush WAL.
> >
> > The only plausible workload I can think of is just calling nextval, and
> the cache pretty much fixes that.
>
> Some users don't want to increase cache setting, do they? Because
>
> - They may expect that setval() affects all subsequent nextval(). But if
> cache is set to greater than one, the value set by setval() doesn't affect
> other backends until they consumed all the cached sequence values.
> - They may expect that the value returned from nextval() is basically
> increased monotonically. If cache is set to greater than one, subsequent
> nextval() can easily return smaller value than one returned by previous
> nextval().
> - They may want to avoid "hole" of a sequence as much as possible, e.g.,
> as far as the server is running normally. If cache is set to greater than
> one, such "hole" can happen even thought the server doesn't crash yet.
>
>
> > FWIW I plan to explore the idea of looking at sequence page LSN, and
> flushing up to that position.
>
> Sounds great, thanks!
>
> Regards,
>
> --
> Fujii Masao
> Advanced Computing Technology Center
> Research and Development Headquarters
> NTT DATA CORPORATION
>
>
>

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