Can we tweak pg_rewind to take differential backups in PostgreSQL?
I was wondering can we hack the pg_rewind code to print the details of the file which have been modified compared to a target server. The list output can then be used for taking differential backups.
Or perhaps we can add an option/switch in pg_rewind --action
--action=print ---> would print the files which have changed
--action=sync ---> would sync them
--action=copy ---> with this option I can specify an additional optino --target-dir where I can copy the files which have changed
This discussion is not really adapted on hackers as pg_rewind is not included in Postgres core code. Please let's discuss your proposal there. Btw, pg_rewind is not aimed to be used as a tool for a backup facility. You may find easier to use existing backup solutions instead, or help out with an in-core solution. There was actually not so long ago a patch to implement in-core differential backups, with a part called profiles able to fetch back the list of files modified since a given LSN point (only an improvement of the core feature though as that's not mandatory to make the machinery work). The patch has not been added to any of the recent commit fests though.
