Comment by magicalhippo

From what I can gather, yes[1]:

A dump/reload of the database or use of the pg_upgrade application is required for major upgrades.

Now, seems one can mostly use pg_upgrade, which only rewrites the system tables[2] so is fairly quick. But if on-disk format has changed it seems you're forced to dump and reload.

At work we've mainly been using SQLAnywhere, which would just disable new functionality for databases using old on-disk format. So upgrading major versions has usually been fairly painless and quick.

[1]: https://www.postgresql.org/support/versioning/

[2]: https://www.postgresql.org/docs/current/pgupgrade.html