Re: Remove Deprecated Exclusive Backup Mode

Bruce Momjian <bruce@momjian.us>

From: Bruce Momjian <bruce@momjian.us>
To: David Steele <david@pgmasters.net>
Cc: Robert Haas <robertmhaas@gmail.com>, Magnus Hagander <magnus@hagander.net>, Stephen Frost <sfrost@snowman.net>, Laurenz Albe <laurenz.albe@cybertec.at>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2020-07-01T20:32:48Z
Lists: pgsql-hackers

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  1. Remove exclusive backup mode

On Wed, Jul  1, 2020 at 04:27:58PM -0400, David Steele wrote:
> On 7/1/20 3:58 PM, Robert Haas wrote:
> > If we could jigger things so that you don't need to stop the backup at
> > all, you only start it, and whether you ever finish copying everything
> > is something about which the system need not know or care, that would
> > be a lot nicer. I'm not sure I see how to do that, though.
> 
> Well, the only thing pg_stop_backup() *really* needs to know is the starting
> WAL position. pg_start_backup() gets that info so if it passes it back to
> pg_stop_backup() that could be enough. Or as was proposed above, it just

Doesn't pg_start_backup already return this?

	SELECT pg_start_backup('test');
	 pg_start_backup
	-----------------
-->	 0/2000028

> Here's a thought. What if we just stored the oldest starting LSN and a count
> of how many backups have been requested. When the backup ends it checks that
> backup count is > 0 and starting LSN is <= its starting LSN. If not, it
> throws an error. When backups go to 0 FPWs are turned off if they were off
> before the first backup.

Can't we just error out of an exclusive-style backup is requested to
start and a previous exclusive-style backup has not been stopped?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

  The usefulness of a cup is in its emptiness, Bruce Lee