PG does not have a concept of incremental backup. The way it works in Oracle and other RDBMS is that incremental backup only backups up changed blocks since the last full backup. So if only 10% of blocks changed since the last full backup, incremental backup will be only for 10%. I am wondering whether it is technically feasible to implement it like this:
Have you seen pg_probackup ? It's in development stage and needs somebody to test it.
1 - At the time of full backup, note the last modified time of each data file in a repository. 2 - Next time when incremental backup runs, for every data file it will check the last modified time of it with the one in the repository to determine whether it has changed since last full backup. If yes, back it up.
Now on to restore:
1 - First restore full backup. 2 - Restore incremental backup.