Re: [patch] demote - Mailing list pgsql-hackers

From Andres Freund
Subject Re: [patch] demote
Date
Msg-id 20200714194951.rzn5yohwwgdo733q@alap3.anarazel.de
Whole thread Raw
In response to Re: [patch] demote  (Amul Sul <sulamul@gmail.com>)
Responses Re: [patch] demote  (Jehan-Guillaume de Rorthais <jgdr@dalibo.com>)
List pgsql-hackers
Hi,

On 2020-07-14 17:26:37 +0530, Amul Sul wrote:
> On Mon, Jul 13, 2020 at 8:35 PM Jehan-Guillaume de Rorthais
> <jgdr@dalibo.com> wrote:
> >
> > Hi,
> >
> > Another summary + patch + tests.
> >
> > This patch supports 2PC. The goal is to keep them safe during demote/promote
> > actions so they can be committed/rollbacked later on a primary. See tests.
> >
> 
> Wondering is it necessary to clear prepared transactions from shared memory?
> Can't simply skip clearing and restoring prepared transactions while demoting?

Recovery doesn't use the normal PGXACT/PGPROC mechanisms to store
transaction state. So I don't think it'd be correct to leave them around
in their previous state. We'd likely end up with incorrect snapshots
if a demoted node later gets promoted...

Greetings,

Andres Freund



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