Hi Maxim, > Secondly, shouldn't we introduce a new WAL record type in order to > make the code backward compatible with previous PG versions? I'm not > 100% sure how the upgrade procedure works in all the details. If it > requires the DBMS to be gracefully shut down before the upgrade then > we are probably fine here.
After reading [1] carefully it looks like we shouldn't worry about this. The upgrade procedure explicitly requires to run `pg_ctl stop` during step 8 of the upgrade procedure, i.e. not in the immediate mode [2]. It also has explicit instructions regarding the replicas. From what I can tell there is no way they will see WAL records they wouldn't understand. [1]: https://www.postgresql.org/docs/current/pgupgrade.html [2]: https://www.postgresql.org/docs/current/app-pg-ctl.html -- Best regards, Aleksander Alekseev
