I performed an upgrade from 1.30 to 1.33 and as a result seem to have lost a lot of content from the Template namespace from rendering properly; for example, looking at https://segaretro.org/Kamen_Rider_555 you'll see that many of the templates which support the page are outright broken. How do I recover these?
Topic on Project:Support desk
the link does not appear to go to a mediawiki install?
Sorry about that--basically, I've had to leave the site down because leaving it up with so much broken content overwhelms the server and spikes my usage almost immediately. Essentially, what's happened is that revisions appear to have "disappeared" after converting the database from 1.30 to 1.33 and looking through the archive/page/text tables, I can't seem to find things matching up any longer. I'm confused as to how this happened, because I've run the wiki for 9 years without incident, and am even more concerned about a 15-year-old install that I need to update--I want to ensure this doesn't happen there, too, obviously. What in the upgrade process would cause these revisions to get stranded and apparently deleted?
if the revisions were imported, could be https://phabricator.wikimedia.org/T232273 . Try running cleanupUsersWithNoId.php followed by migrateActors.php and see if that fixes anything
See MediaWiki 1.33#Known issues. Sadly, upgrading from old version to 1.33 has proved to be a fiasco... hopefully some of those problems get fixed on 1.33.1 eventually...
Seeing the reports here, I would recommend not to upgrade to MediaWiki 1.33 now.
However, if you "only" want to have an up-to-date installation again, for which you can get security updates and everthing, then you might want to take a look at MediaWiki 1.31. MediaWiki 1.31 is a version with Long Term Support, which will still be supported as long as MediaWiki 1.33 will be supported as well. Maybe it is an option to update to MediaWiki 1.31, instead?
So, there is a workaround in the event your wiki also breaks and loses its mind!
Set $wgActorTableSchemaMigrationStage = SCHEMA_COMPAT_OLD; and this will use the pre-upgrade schema, giving you a way to pull the data back out and load into a fresh instance.