CAUTION
When I updated PL9 to 9.2.0 and/or 9.2.1, the database was silently changed.
Now, if one wants to restore an earlier release, the database is set aside and a new empty database is created, which means that one might loose edits, keywords, metadata etc. - if sidecars haven’t been saved. Please note that the set aside copy can’t be used to populate the new database. Things are pretty much thought and built one-way here.
If sidecar settings are left in their default, customizing will be re-added to the fresh database every time a folder with images is selected. Metadata has to be re-read manually because metadata is not sync’ed by default.
The downside of a fresh database is, that it will not include all images and data, which harms search, projects, history and whatever is not saved in the sidecars by PL (Mac/Win).
To prevent such issues, I recommend to have PL create a database backup before each update. For easier fallback, duplicate PL and update the copy or back up the installer.
On Win, things might be different.