backup failed with "ERROR: query failed: ERROR: function pg_control_system() does not exist"

[rtau-t24]

We are trying to backup the PostgreSQL 9.5 database with pg_probackup 2.0.11 but when trying to run the backup, the following error was encountered:

LOG: (query) show archive_command
LOG: (query) SELECT system_identifier FROM pg_control_system()
ERROR: query failed: ERROR: function pg_control_system() does not exist
LINE 1: SELECT system_identifier FROM pg_control_system()
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
query was: SELECT system_identifier FROM pg_control_system()

In addition, it seems that the function pg_control_system() does not exist in 9.5, but only 9.6 and newer.

[za-arthur]

Thank you for the issue!
Yeah it is definitely a bug. PostgreSQL hasn't pg_control_system().

[za-arthur]

I changed the function a little bit. Now it checks system_identifier for PostgreSQL 9.5 using pg_read_binary_file().