digikam 8.1 - problem with migration mysql > sqlite

[Maik Qualmann]

No, we do not plan to migrate the face, thumbnail or similarity database. 
These databases tend to contain temporary information that can be restored 
from the core database at any time using the maintenance tool.
The face recognition database (training database) should be rebuilt anyway 
when we made changes to the face engine.

Maik

Am Dienstag, 15. August 2023, 22:24:02 CEST schrieben Sie:
> Hi Maik ,
> 
> 
> Ok, thank you for the explanation.
> However, this is something that will be implemented ?
> There is any reason for this database not to be migrated?
> 
> Because took a long time to scan all my photos (+700GBytes) to rebuild and
> I really don't want to run this again.
> 
> 
> Em seg., 14 de ago. de 2023 às 13:47, Maik Qualmann <metzpinguin at gmail.com>
> 
> escreveu:
> > The behavior is normal, the face database and thumbnail database are not
> > migrated.
> > Go into the maintenance tool, enable the face detection/recognition
> > section
> > and check the box to rebuild the training database. Based on all confirmed
> > faces, the facial recognition database is rebuilt.
> > 
> > Maik
> > 
> > Am Montag, 14. August 2023, 15:03:51 CEST schrieb Cesar Inacio Martins:
> > > Hi,
> > > 
> > > After a couple of years without using my DK, I finally returned to it.
> > > 
> > > So, I've upgraded from version 7.4 to 8.1.
> > > I used the Internal MySQL before because I have ~80k photos.
> > > Now, to solve an old issue with face recognition, I decided to rerun it
> > > over all my albums to exclude the faces from all photos and detect all
> > > again ( not people, yet, only detect faces).
> > > I've done that using MySQL as a database.
> > > 
> > > During this process, rereading the manuals, I saw there is an essential
> > > improvement on sqlite, where it became recommended even for libraries
> > 
> > with
> > 
> > > ~100k photos.
> > > 
> > > When I finished all face recognition, which took ~ 1 week, I migrate my
> > > database back to sqlite.
> > > The migration ran fine.
> > > However, when I set the DK to sqlite and put my albums to now recognize
> > 
> > the
> > 
> > > faces, they give the error message : "face recognition is aborted,
> > 
> > because
> > 
> > > there are no identities to recognize. Please add new identities"
> > > 
> > > Then I connected both databases and did a count(*) on tables and see at
> > > recognition.db, no data was imported.
> > > I tried this migration twice, one with WAL enabled and the second
> > > attempt
> > > with it disabled.
> > > 
> > > Is that expected or is it a defect?
> > > 
> > > 
> > > MySQL
> > > 
> > > > Settings          |count(*)|
> > > > ------------------+--------+
> > > > Settings          |      20|
> > > > Identities        |     148|
> > > > IdentityAttributes|     444|
> > > > FaceMatrices      |   14687|
> > > > KDTree            |       0|
> > > 
> > > SQLite - after migration
> > > 
> > > > "Settings"        |count(*)|
> > > > ------------------+--------+
> > > > Settings          |       2|
> > > > Identities        |       0|
> > > > IdentityAttributes|       0|
> > > > FaceMatrices      |       0|
> > > > KDTree            |       0|