| From: | Jehan-Guillaume de Rorthais <jgdr(at)dalibo(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Amul Sul <sulamul(at)gmail(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 21:16:34 |
| Message-ID: | 20200714231634.7cad6815@firost |
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| Lists: | pgsql-hackers |
On Tue, 14 Jul 2020 12:49:51 -0700
Andres Freund <andres(at)anarazel(dot)de> wrote:
> 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(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...
Indeed. I experienced it while debugging. PGXACT/PGPROC/locks need to
be cleared.
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