Re: [patch] demote

From: Andres Freund <andres(at)anarazel(dot)de>
To: Amul Sul <sulamul(at)gmail(dot)com>
Cc: Jehan-Guillaume de Rorthais <jgdr(at)dalibo(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>
Subject: Re: [patch] demote
Date: 2020-07-14 19:49:51
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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(at)dalibo(dot)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...


Andres Freund

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