I'm implementing incremental backups using filesystem-level snapshots.
pg_stop_backup() can be used to this end. Via these pair of functions or via the
backup_label file, I can identify the "START WAL LOCATION" and "STOP WAL LOCATION" and associated files. The problem is, when these files are not the same and not strictly consecutive (ie, there are intervening files), how do I deterministically determine them? While it might be the case that the files are monotonically increasing, how can I be sure that is the case, and how can I be sure I've located all the intervening files? Can I be guaranteed the files will be written or changed in chronological order? Or in lexicographical order? (From what I've seen, neither is the case.)
After 3x reading the documentation, I can't get any clarity or resolution on this: it tells us that the backup process must include these files, but offers no indication on how to identify them! If I've overlooked a page in the documentation, I'd appreciate being it pointed out.
BTW: Please don't tell me to use
pg_basebackup unless you want a kick in the face.
BTW2: I'm trying to make a complete backup set without doing a full backup. Barman stores the archive logs somewhere else, which is what I want to avoid. Even if I implemented barman (which I don't want to), I'd still need to know which files I need for the backup during its operation.