Re: Remove Deprecated Exclusive Backup Mode

On Wed, 2020-07-01 at 16:46 -0400, Stephen Frost wrote:
> I continue to find it curious that we stress a great deal over (very
> likely) poorly written backup scripts that haven't been updated in the
> 5+? years since exclusive mode was deprecated, but we happily add new
> keywords in new major versions and remove columns in our catalog tables
> or rename columns or entirely redo how recovery works (breaking every
> script out there that performed a restore..) or do any number of other
> things that potentially break applications that communicate through the
> PG protocol and other parts of the system that very likely have scripts
> that were written to work with them.
> 
> I'm really of the opinion that we need to stop doing that.
> 
> If someone could explain what is so special about *this* part of the
> system that we absolutely can't possibly accept any change that might
> break user's scripts, and why it's worth all of the angst, maintenance,
> ridiculously difficult documentation to understand and hacks (the
> interface to pg_start_backup is ridiculously warty because of this), I'd
> greatly appreciate it.

Easy.  Lots of people write backup scripts, and fewer people write
complicated pg_catalog queries.  We would make way more users unhappy.

Besides, there is nothing "poorly written" about a backup script using
exclusive backup as long as the user is aware that there could be some
small degree of trouble in case of a crash.

You have a point about reworking the way recovery works: after teaching
several classes and running into oddities with recovery parameters in
postgresql.conf, I am not sure if that was a good move.
Particularly the necessity for "recovery.signal" makes the New Way no
easier than the Old Way - perhaps something like "pg_ctl start_in_recovery"
would have been smarter.

But one instance where we made users unhappy is not justification
for making them unhappy again.

Yours,
Laurenz Albe