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From: David Steele <[email protected]>
To: Nathan Bossart <[email protected]>
To: Chapman Flack <[email protected]>
Cc: Stephen Frost <[email protected]>
Cc: [email protected]
Subject: Re: Postgres restart in the middle of exclusive backup and the presence of backup_label file
Date: Tue, 8 Mar 2022 15:09:50 -0600
Message-ID: <[email protected]> (raw)
In-Reply-To: <20220308200107.GA85558@nathanxps13>
References: <[email protected]>
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	<[email protected]>
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	<20220302010302.GA1182956@nathanxps13>
	<[email protected]>
	<20220308200107.GA85558@nathanxps13>

On 3/8/22 14:01, Nathan Bossart wrote:
> On Wed, Mar 02, 2022 at 02:23:51PM -0500, Chapman Flack wrote:
>> I did not notice this earlier (sorry), but there seems to remain in
>> backup.sgml a programlisting example that shows a psql invocation
>> for pg_backup_start, then a tar command, then another psql invocation
>> for pg_backup_stop.
>>
>> I think that was only workable for the exclusive mode, and now it is
>> necessary to issue pg_backup_start and pg_backup_stop in the same session.
>>
>> (The 'touch backup_in_progress' business seems a bit bogus now too,
>> suggesting an exclusivity remembered from bygone days.)
>>
>> I am not sure what a workable, simple example ought to look like.
>> Maybe a single psql script issuing the pg_backup_start and the
>> pg_backup_stop, with a tar command in between with \! ?
>>
>> Several bricks shy of production-ready, but it would give the idea.
> 
> Another option might be to just remove this section.  The top of the
> section mentions that this is easily done using pg_basebackup with the -X
> parameter.  The bottom part of the section includes more complicated steps
> for when "more flexibility in copying the backup files is needed..."
> AFAICT the more complicated strategy was around before pg_basebackup, and
> the pg_basebackup recommendation was added in 2012 as part of 920febd.
> Thoughts?

This makes sense to me. I think pg_basebackup is far preferable to doing 
anything like what is described in this section. Unless you are planning 
to do something fancy (parallelization, snapshots, object stores, etc.) 
then pg_basebackup is the way to go.

Regards,
-David

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