| From: | "Drouvot, Bertrand" <bertranddrouvot(dot)pg(at)gmail(dot)com> |
|---|---|
| To: | shveta malik <shveta(dot)malik(at)gmail(dot)com>, "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com> |
| Cc: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Ajin Cherian <itsajin(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Subject: | Re: Synchronizing slots from primary to standby |
| Date: | 2023-09-22 12:30:59 |
| Message-ID: | 17aeb17c-73b7-4038-801a-0edbcdf1fb96@gmail.com |
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| Lists: | pgsql-hackers |
Hi,
Thanks for all the work that has been done on this feature, and sorry
to have been quiet on it for so long.
On 9/18/23 12:22 PM, shveta malik wrote:
> On Wed, Sep 13, 2023 at 4:48 PM Hayato Kuroda (Fujitsu)
> <kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
>> Right, but I wanted to know why it is needed. One motivation seemed to know the
>> WAL location of physical standby, but I thought that struct WalSnd.apply could
>> be also used. Is it bad to assume that the physical walsender always exists?
>>
>
> We do not plan to target this case where physical slot is not created
> between primary and physical-standby in the first draft. In such a
> case, slot-synchronization will be skipped for the time being. We can
> extend this functionality (if needed) later.
>
I do think it's needed to extend this functionality. Having physical slot
created sounds like a (too?) strong requirement as:
- It has not been a requirement for Logical decoding on standby so that could sounds weird
to require it for sync slot (while it's not allowed to logical decode from sync slots)
- One could want to limit the WAL space used on the primary
It seems that the "skipping sync as primary_slot_name not set." warning message is emitted
every 10ms, that seems too verbose to me.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
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