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From: Amit Kapila <amit.kapila16@gmail.com>
Date: Wed, 24 Jan 2024 11:13:31 +0530
Message-ID: 
 <CAA4eK1LMfoDbo4CfoW9tMDWYRZwQ+paF_wrD9=WiXJR3mkm7Pg@mail.gmail.com>
Subject: Re: Synchronizing slots from primary to standby
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: shveta malik <shveta.malik@gmail.com>,
 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>,
	"Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>,
 Dilip Kumar <dilipbalaut@gmail.com>,
	Peter Smith <smithpb2250@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>,
	"Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>,
	Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>,
	Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
 Bruce Momjian <bruce@momjian.us>,
	Ashutosh Sharma <ashu.coek88@gmail.com>, Andres Freund <andres@anarazel.de>,
	pgsql-hackers <pgsql-hackers@postgresql.org>,
 Ajin Cherian <itsajin@gmail.com>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>
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On Wed, Jan 24, 2024 at 10:41=E2=80=AFAM Masahiko Sawada <sawada.mshk@gmail=
.com> wrote:
>
> On Mon, Jan 22, 2024 at 3:58=E2=80=AFPM Amit Kapila <amit.kapila16@gmail.=
com> wrote:
> >
> > Can we think of using GetStandbyFlushRecPtr()? We probably need to
> > expose this function, if this works for the required purpose.
>
> GetStandbyFlushRecPtr() seems good. But do we really want to raise an
> ERROR in this case? IIUC this case could happen often when the slot
> used by the standby is not listed in standby_slot_names.
>

or it can be due to some bug in the code as well.

> I think we
> can just skip such a slot to synchronize and check it the next time.
>

How about logging the message and then skipping the sync step? This
will at least make users aware that they could be missing to set
standby_slot_names.

> Here are random comments on slotsyncworker.c (v66):
>
> +/* GUC variable */
> +bool       enable_syncslot =3D false;
>
> Is enable_syncslot a really good name? We use "enable" prefix only for
> planner parameters such as enable_seqscan, and it seems to me that
> "slot" is not specific. Other candidates are:
>
> * synchronize_replication_slots =3D on|off
> * synchronize_failover_slots =3D on|off
>

I would prefer the second one. Would it be better to just say
sync_failover_slots?

--=20
With Regards,
Amit Kapila.