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From: David Steele <[email protected]>
To: Robert Haas <[email protected]>
Cc: Thomas Munro <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Pg Hackers <[email protected]>
Cc: Stephen Frost <[email protected]>
Subject: Re: The danger of deleting backup_label
Date: Mon, 16 Oct 2023 19:45:35 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+TgmoYYcGC-aErHmYyqggST4Q5SKqeZDxikgg_BTi=3tZGJQw@mail.gmail.com>
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On 10/16/23 15:06, Robert Haas wrote:
> On Mon, Oct 16, 2023 at 1:00 PM David Steele <[email protected]> wrote:
>> After some agonizing (we hope) they decide to delete backup_label and,
>> wow, it just works! So now they merrily go on their way with a corrupted
>> cluster. They also remember for the next time that deleting backup_label
>> is definitely a good procedure.
>>
>> The idea behind this patch is that deleting backup_label would produce a
>> hard error because pg_control would be missing as well (if the backup
>> software did its job). If both pg_control and backup_label are present
>> (but pg_control has not been loaded with the contents of backup_label,
>> i.e. it is the running copy from the backup cluster) we can also error.
> 
> I mean, I think we're just going in circles, here. I did and do
> understand, but I didn't and don't agree. You're hypothesizing a user
> who is willing to do ONE thing that they shouldn't do during backup
> restoration (namely, remove backup_label) but who won't be willing to
> do a SECOND thing that they shouldn't do during backup restoration
> (namely, run pg_resetwal). 

In my experience the first case is much more likely than the second. 
Your experience may vary.

Anyway, I think they are pretty different. Deleting backup label appears 
to give a perfectly valid restore. Running pg_resetwal is more clearly 
(I think) the nuclear solution.

> I understand that you feel differently, and that's fine, but I don't
> think our disagreement here stems from me being confused. I just ...
> don't agree.

Fair enough, we don't agree.

Regards,
-David

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