I have not ran MySQL for some years but it at least used to have exactly the same issue. Upgrading a database with MySQL can take a long time if you have many tables. The main difference is only really that PostgreSQL does it with a separate tool, pg_upgrade, while MySQL does it as part of the main binary.

For both MySQL and PostgreSQL you will need to use some kind of logical upgrades if you want no downtime.

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boxed 3 hours ago | parent | next [-]

They don't change the on-disk structure all the time though...

	▲	jeltz 14 minutes ago \| parent [-]
		Mostly because MySQL development is slower.

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tomnipotent 4 hours ago | parent | prev [-]

MySQL has advocated for decades spinning up a replica with the upgraded version, waiting for it to catch up to master before promoting it to the new master. You can do the same thing with Postgres.

	▲	jeltz 3 hours ago \| parent [-]
		Exactly, MySQL and PostgreSQL are the same here. Maybe one is a bit faster than the other at doing major version upgrades but the behaviours are quite similar.