Re: Remove Deprecated Exclusive Backup Mode

On 12/11/18 5:24 PM, David Steele wrote:
> 
> Attached is the patch.
> 
> I was a bit surprised by how much code went away.  There was a lot of
> code dedicated to making sure that backup_label got renamed on shutdown,
> that there was not an exclusive backup running, etc.
> 
> There were no tests for exclusive backup so the test changes were minimal.
> 
> I did have to replace one "hot backup" in
> 010_logical_decoding_timelines.pl.  I'm not sure why the backup was
> being done this way, or why the standby needs a copy of pg_replslot
> (which is not copied by pg_basebackup).  It might be worth looking at
> but it seemed out of scope for this patch.

Rebased patch is attached.

I also fixed the issue that Robert pointed out with regard to changing 
the function signatures. It's a bit weird that there are optional 
parameters when the last parameter is really not optional (i.e. the 
default will lead to an error). Any suggestions are appreciated.

Reading back through the thread, the major objection to the original 
patch was that it was submitted too soon. Hopefully the elapsed time 
addresses that concern.

Another common objection is that the new API is hard to use from bash 
scripts. This is arguably still true, but Laurenz has demonstrated that 
bash is capable of this feat:

https://github.com/cybertec-postgresql/safe-backup

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.

Regards,
-- 
-David
david@pgmasters.net