PostgreSQL 15: changes in the low level backup functions

The upcoming PostgreSQL 15 release implements a few changes into the /low level/ backup functions.
Nowdays I suspect nobody, except backup solution developers, know or use such functions, but I clearly remember when we developed our own scripts to do a continuos backup using functions like pg_start_backup() and pg_stop_backup().
You should use other backup solutions today, like the great pgBackRest.
In any case, what are the changes?
As you can read from [the release notes](https://www.postgresql.org/docs/15/release-15.html{:target=”_blank”} there two mainly:

1. functions have been renamed to a more consistent naming scheme.
2. a few functions and modes have been removed.

The functions are now named as pg_backup_, so pg_start_backup() becomes pg_backup_start(), and similarly, pg_stop_backup() becomes pg_backup_stop(). Quite frankly I like this decision, it makes the naming simpler to search for and to remember.
Moreover, there is no more the presence of deprecated (since version 9.6, if I remember correctly), the exclusive backup mode. This was the only way to perform a low level backup back in the days, but since a lot it has been deprecated. One of the problems with exclusive backups is that the system will create a label file that prevents the primary to restart after a crash, and in turn this led people to delete the label file also on standby servers. Now this is no more a problem, and the pg_backup_start() and pg_backup_stop() functions do not handle anymore the exclusive backup parameter.
As a consequence of this choice, the functions pg_is_in_backup() and pg_backup_start_time() have been removed because they were focused only on exclusive backups, that do not exist anymore.