re: backup SQL dumps instead of db files - indeed! In my small experiment (SQL databases in a browser profile, [1]), simple `sqlite3 "$file" .dump | gzip >"$file.sql.gz"` decreased size of files to be backed up about 10 times!
I'm not sure how it compares to Borg's delta- and zstd-compression, though.
hm but can't you do the same thing (gzipping) with the db itself?
Edit. Regardless of if you maybe even meant that, I made a small test too: A 42 MB db zipped is 8.8M, but its sql dump zipped is 4.9M, so almost half the size. Pretty good already. If you don't just `.dump` but actually output the tables in a consistently sorted manner, the size might go down even more and will enable very efficient delta-ing. Questionable value to effort ratio though...
re: gzipping the db itself - yep, I tried and saw the same effect as you did: about half a size. I think it's because of indexes (I once played with sqlite3_analyzer[1] and on some databases it showed about half of disk space was used by indexes) and unused pages (all the space which can be vacuum'ed - again, size of some databases can be decreased almost twice by vacuum'ing).
On the other side, indeed, text dump is likely not the most space-efficient way of storing raw DB data (compared to some binary one), so I wouldn't be surprised to find databases for which gzipped sql dump is bigger than (gzipped) database itself. I would even say that I'm surprised that it's not true for most databases :)
I'm not sure how it compares to Borg's delta- and zstd-compression, though.
[1]: http://alexey.shpakovsky.ru/en/minimizing-size-of-browser-pr...