Message-ID: <e9b4ce8b-5e5e-4076-83f9-23e771e9dfe7@oss.nttdata.com>
Date: Mon, 3 Mar 2025 18:48:41 +0900
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Subject: Re: doc: Mention clock synchronization recommendation for
 hot_standby_feedback
To: Jakub Wartak <jakub.wartak@enterprisedb.com>,
 Amit Kapila <amit.kapila16@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
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From: Fujii Masao <masao.fujii@oss.nttdata.com>
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On 2025/03/03 16:35, Jakub Wartak wrote:
> Hi Amit,
> 
> On Mon, Mar 3, 2025 at 6:26 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> [..]
> 
> OK, sure.
> 
>> How about something like: "Note that if the clock on standby is moved
>> ahead or backward, the feedback message may not be sent at the
>> required interval. This can lead to prolonged risk of not removing
>> dead rows on primary for extended periods as the feedback mechanism is
>> based on timestamp."
> 
> Sure thing. I've just added '(..) In the extreme cases this can..' as
> it is pretty rare to hit it. Patch attached.

When the clock moves forward or backward, couldn't it affect
not only the standby but also the primary? I’m wondering
because TimestampDifferenceExceeds() seems to be used
in several places in addition to hot standby feedback.

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION