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help / color / mirror / Atom feedFrom: Julien Rouhaud <[email protected]>
To: Nitin Jadhav <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: Bharath Rupireddy <[email protected]>
Cc: Bruce Momjian <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Magnus Hagander <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Report checkpoint progress with pg_stat_progress_checkpoint (was: Report checkpoint progress in server logs)
Date: Fri, 18 Feb 2022 01:27:24 +0800
Message-ID: <20220217172724.uhs2v3mgio7y6ga5@jrouhaud> (raw)
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References: <CABUevEyX6-NSnhMhWzicg_PpmF52Fv_Zm7tgLT+9iDAO4W8Ftg@mail.gmail.com>
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Hi,
On Thu, Feb 17, 2022 at 10:39:02PM +0530, Nitin Jadhav wrote:
> > > Thank you for sharing the information. 'triggering backend PID' (int)
> > > - can be stored without any problem.
> >
> > There can be multiple processes triggering a checkpoint, or at least wanting it
> > to happen or happen faster.
>
> Yes. There can be multiple processes but there will be one checkpoint
> operation at a time. So the backend PID corresponds to the current
> checkpoint operation. Let me know if I am missing something.
If there's a checkpoint timed triggered and then someone calls
pg_start_backup() which then wait for the end of the current checkpoint
(possibly after changing the flags), I think the view should reflect that in
some way. Maybe storing an array of (pid, flags) is too much, but at least a
counter with the number of processes actively waiting for the end of the
checkpoint.
> > > 'checkpoint or restartpoint?'
> >
> > Do you actually need to store that? Can't it be inferred from
> > pg_is_in_recovery()?
>
> AFAIK we cannot use pg_is_in_recovery() to predict whether it is a
> checkpoint or restartpoint because if the system exits from recovery
> mode during restartpoint then any query to pg_stat_progress_checkpoint
> view will return it as a checkpoint which is ideally not correct. Please
> correct me if I am wrong.
Recovery ends with an end-of-recovery checkpoint that has to finish before the
promotion can happen, so I don't think that a restart can still be in progress
if pg_is_in_recovery() returns false.
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Subject: Re: Report checkpoint progress with pg_stat_progress_checkpoint (was: Report checkpoint progress in server logs)
In-Reply-To: <20220217172724.uhs2v3mgio7y6ga5@jrouhaud>
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