[davidfor]

Originally Posted by Quoth

I searched with Google rather than Forum search and found
"The database on the device is corrupt. Unless you have a backup you can use, the fix is sign out of the Kobo account on the device and then back in."

To the best of my knowledge, there is no way to recover the database from the error you are seeing. I believe that will only be seen when the actual table data is corrupted. You can recover from some problems, but, mainly ones related to the indexes or free pages in the file.

Any backup is likely ancient. Something I forgot about!

You can automate it with my Kobo Utilities plugin for whenever the device is connected

Thoughts:
A backup likely would be before I annotated/proofed that book anyway and I always import the annotations with Calibre Kobo Utilities, copy& paste as a text file and make a back up that immediately before starting another book.

Edit
I've logged out and logged in and Calibre is doing something. Collections all empty.

If you are using epubs, then the annotations might be in the "Digital Editions/Annotations" directory. These will be read when the book is opened and they are merged with whatever is in the database. Recent firmware makes the database the primary source, but, if there are no entries in the database, whatever is in the file is use.

I looked at copy of database with DB browser for SQlite and did an export then import.
Except either it's too broken, or I need to edit the text as original is about 150M and "new" version about 92k!

If you tried to do that from the corrupt database, that is pretty much what I would expect. It will only have exported the data it could reach. I had another look at this recently because my wife's Forma had a corrupt database. That was one of the things I tried. The signout was the only thing that worked. That plus turning the backup on again.