I'm surprised that there is an immediate cut-off in the more recent database transitions. It seems very onerous that there is not one version of MediaWiki which supports both old and new versions of a database. Cutting over will require at least more complex migration, and probably more downtime, especially for entities not resourced at the level of teh WMF.
Topic on Talk:Compatibility/Flow
@Rich Farmbrough Are you referring to MariaDB? Note that "MariaDB 10.1.0+" specifies a minimum version with the plus sign to mean "and later". This thus includes overlap to MariaDB 10.3.
Unlike PHP itself, MySQL and MariaDB follow semver, which means minor versions introduce new behaviours without changing or break existing contracts. As such, even MediaWIki versions that were released before MariaDB 10.3 existed, should be able to work on it, given we tested it with MariaDB 10.1. That's why we promise "and later", because we tested it with MariaDB 10.1, and upstream MariaDB follows semver.
Later MediaWiki versions may start to assume and depend on those newer behaviours, at which point we raise the minimum requirement.
If MariaDB did not follow semver, and if our past versions could only promise support for MariaDB 10.1.x exactly, then we'd indeed need to "introduce" support for MariaDB 10.3.x at some point and leave overlap. I hope this explains why that is not the case / not needed.
Thanks, the full implications (and indeed meaning) of the + sign were lost on me. It's not clear that it applies to the last two components, rather than just one or the whole thing. Rich Farmbrough 14:43, 15 October 2024 (UTC).