bad behavior of --keep-data-generations 0

[thoshiai]

When pg_rman backup with --keep-data-generations 0, all backup that
contain current backup is deleted. The cause of this behavior is that
pg_rman allow for KEEP_DATA_GENERATIONS to 0.

 $ psql --version
 psql (PostgreSQL) 13.1
 $ pg_rman --version
 pg_rman 1.3.13
 
 $ pg_rman backup -b full -d postgres --keep-data-generations 1
 INFO: copying database files
 INFO: copying archived WAL files
 INFO: backup complete
 INFO: Please execute 'pg_rman validate' to verify the files are correctly copied.
 INFO: start deleting old backup (keep generations = 1)
 INFO: does not include the backup just taken 
$ pg_rman show
 =====================================================================
  StartTime           EndTime              Mode    Size   TLI  Status
 =====================================================================
 2021-10-14 12:37:40  2021-10-14 12:37:42  FULL   352MB     1  DONE
 $ pg_rman backup -b full -d postgres --keep-data-generations 0
 INFO: copying database files
 INFO: copying archived WAL files
 INFO: backup complete
 INFO: Please execute 'pg_rman validate' to verify the files are correctly copied.
 INFO: start deleting old backup (keep generations = 0)
 INFO: delete the backup with start time: "2021-10-14 12:37:53"
 INFO: delete the backup with start time: "2021-10-14 12:37:40" 
 $ pg_rman show 
 =====================================================================
  StartTime           EndTime              Mode    Size   TLI  Status
 =====================================================================

[huangfumingyue]

Thank you for your issue.
First, if you set --keep-data-generations to 0, deleting all backup files is the correct behavior.
And I think it's useful if the user want to delete all backup files.
According to the current specifications of pg_rman, if user want to delete all backup files,
It will takes a lot of time because user have to manually delete all the files from the backup catalog.

So, I think we will still allowing --keep-data-generations to be 0,
How about adding this case to the manual as restrictions?

[thoshiai]

Thank you for your answer. I think that your idea is good!

I'm worried about the behavior when the this parameter set 0. For example,
if it sets 0, all backup file are deleted, including backup which status set DONE( not OK).
Is this behavior no problem?

[huangfumingyue]

I think it is no probolem.
「DONE」means backup is done successfully, but we does not do validate yet.
If validation checks are not done,Only the restore and the next increment are affected.
so,If we delete all backup files including backup files with status 'DONE',
the next time you get the full backup, there is no problem.