Re: Remove Deprecated Exclusive Backup Mode

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: David Steele <david(at)pgmasters(dot)net>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Remove Deprecated Exclusive Backup Mode
Date: 2020-06-30 22:13:30
Message-ID: 20200630221330.GJ3125@tamriel.snowman.net
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Greetings,

* David Steele (david(at)pgmasters(dot)net) wrote:
> Lastly, there is some concern about getting the backup label too late when
> doing snapshots or using traditional backup software. It would certainly be
> possible to return the backup_label and tablespace_map from
> pg_start_backup() and let the user make the choice about what to do with
> them. Any of these methods will require some scripting so I don't see why
> the files couldn't be written as, for example, backup_label.snap and
> tablespace_map.snap and then renamed by the restore script. The patch does
> not currently make this change, but it could be added pretty easily if that
> overcomes this objection.

Of course, if someone just restored that snapshot without actually
moving the files into place they'd get a corrupted database without any
indication of anything being wrong...

And if we checked for those files on startup and complained about them
being there (called .snap) then we're back into the "crash during backup
causes PG to fail to start" situation.

All of which is, as I recall, is why we have the API we do today.

As such, doing that doesn't strike me as an improvement over using the
new API and making it abundently clear that it's not so simple as people
might like to think it is...

Thanks,

Stephen

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