Thank you, Laurenz. Yes, I say binary dump/restore would be faster because of the -j option.
Well, I suppose there's no certainty of what might break without going through the whole process. On Fri, Sep 26, 2025 at 7:57 PM Laurenz Albe <[email protected]> wrote: > On Fri, 2025-09-26 at 17:48 +0530, Ashish Mukherjee wrote: > > I have a strange requirement to downgrade from pgsql 17 to pgsql 12. > This is > > because we found in production certain incompatibilities between both > versions > > for our database. It should have been caught in testing but was not. > > > > The clean way seems to be text file dump and restore but this would be > too > > huge and too slow for our database of 3T. If I use pg_dump v17 and then > > restore with pg_restore v 17 on a pgsql v12 database, is there any risk? > > Yes, there is the risk that the restore will fail. > Downgrading is not supported. > > That's why the best way to do it is a plain format dump: you can edit the > dump file to manually fix any errors. > I am surprised that you think that restoring a plain format dump would > be significantly slower than restoring a different format (unless you are > talking about parallel restore with -j). > > > I tried a small test with a bunch of tables and it worked, but am > wondering > > about the pitfalls. I am restoring from the directory format dump. > > Anything can happen... > > > When I do dump/restore like this for a test table, I get the following > errors > > during restore but the table gets restored fine. > > > > pg_restore: error: while PROCESSING TOC: > > error: pg_restore: error: pg_restore: from TOC entry 17168; 1259 > 58572315 TABLE pkgs s14 > > pg_restore: error: pg_restore: pg_restore: pg_restore: from TOC entry > 17168; 1259 58572315 TABLE pkgs s14 > > pg_restore: error: pg_restore: from TOC entry 17168; 1259 58572315 > TABLE pkgs s14 > > pg_restore: error: pg_restore: from TOC entry 17168; 1259 58572315 TABLE > pkgs s14 > > error: from TOC entry 17168; 1259 58572315 TABLE pkgs s14 > > pg_restore: warning: errors ignored on restore: 2 > > > > pkgs is the table and s14 is my database > > There should be more: the actual error messages. These will give you a > clue. > > Yours, > Laurenz Albe >
