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Date: Wed, 15 Feb 2023 15:21:13 +0100
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Subject: Re: Minimal logical decoding on standbys
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To: Ashutosh Sharma <ashu.coek88@gmail.com>,
 Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>, Thomas Munro
 <thomas.munro@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>,
 Ibrar Ahmed <ibrar.ahmad@gmail.com>, Amit Khandekar
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 tushar <tushar.ahuja@enterprisedb.com>,
 Rahila Syed <rahila.syed@2ndquadrant.com>,
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From: "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com>
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Hi,

On 2/15/23 1:32 PM, Ashutosh Sharma wrote:
> Thanks Andres. I have one more query (both for you and Bertrand). I
> don't know if this has already been answered somewhere in this mail
> thread, if yes, please let me know the mail that answers this query.
> 
> Will there be a problem if we mandate the use of physical replication
> slots and hot_standby_feedback to support minimum LD on standby. 

I don't think we have to make it mandatory. There is use cases
where it's not needed and mentioned by Andres up-thread [1] (see the comment
"The patch deals with this...")

> I know people can do a physical replication setup without a replication
> slot or even with hot_standby_feedback turned off, but are we going to
> have any issue if we ask them to use a physical replication slot and
> turn on hot_standby_feedback for LD on standby. This will reduce the
> code changes required to do conflict handling for logical slots on
> standby which is being done by v50-0001 and v50-0002* patches
> currently.
> 

But on the other hand we'd need to ensure that the primary physical slot
and HSF set to on on the standby are always in place. That would probably lead
to extra code too.

I'm -1 on that but +1 on the fact that it should be documented (as done in 0006).

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

[1]: https://www.postgresql.org/message-id/20211028210755.afmwcvpo6ajwdx6n%40alap3.anarazel.de