On Tue, Jul 7, 2020 at 1:18 PM Alvaro Herrera <alvhe...@2ndquadrant.com> wrote: > Yeah, backporting GUCs is not a big deal. Sure, the GUC won't appear in > postgresql.conf files generated by initdb prior to the release that > introduces it. But users that need it can just edit their .confs and > add the appropriate line, or just do ALTER SYSTEM after the minor > upgrade.
I don't buy that argument myself. At a minimum, if we do it then we ought to feel bad about it. It should be rare. The fact that you can have a replica on an earlier point release enforces the idea that it ought to be broadly compatible. Technically users are not guaranteed that this will work, just like there are no guarantees about WAL compatibility across point releases. We nevertheless tacitly provide a "soft" guarantee that we won't break WAL -- and that we won't add entirely new GUCs in a point release. -- Peter Geoghegan
