Migrate from Linux to Mac

[Gilles Caulier]

Hi,

The group definitions are stored in the digiKam database. If the group
is stored as duplicate in the XMP sidecar, the group restoration must
be transparent. I think that it's not the case (i don't remember doing
it in the past). Perhaps Maik can second me here...

Anyway, the digiKam XMP namespace does not contain anything about
group properties :

https://exiftool.org/TagNames/XMP.html#digiKam

If group properties must be stored in XMP, it must be by priority in
the digiKam namespace (where we can do what we want), and in second to
another XMP standard XMP namespace, if these properties exist and are
not proprietary (a.k.a photoshop for ex.).

In the database the group properties will define the list of joined items.

A script can help to restore/patch the properties in the database. The
schema is documented here :

https://invent.kde.org/graphics/digikam/-/blob/master/project/documents/DBSCHEMA.ODS?ref_type=heads

if i'm not too wrong the table is this one:

Table « ImageRelations »

NAME    TYPE    DESCRIPTION    READ FROM    WRITTEN  TO    CHANGED BY
subject    INTEGER FOREIGN KEY
object    INTEGER FOREIGN KEY
type    INTEGER

So the item grouping uses the item ID in the database, not the file
path. When you create a new database by importing the collections to a
new computer, file and sidecar are parsed to restore the properties.
Each item imported in the new database will use a new ID, which will
break the grouping feature. And as the grouped item list is not stored
in XMP...

Voilà for a quick interpretation of the problematic (without double
check in the source code).

Best regards

Gilles



Le mer. 12 nov. 2025 à 13:54, Willem Boers <wboers at xs4all.nl> a écrit :
>
> I am currently using DigiKam on a Ubuntu Linux PC using the local MySQL Server on this machine. All collections (>100k photo and video files) and the database are on a SSD on this PC.
> I use sidecar XMP files to store metadata for all RAW files and video files and I am only using the basic DigiKam functions for tagging and labeling (no RAW processing, editing or face recognition)
> The Linux PC will be deprecated and I want to migrate everything to my Apple Mac mini. I have done some tests and it appears that DigiKam is working perfectly well on my Mac even with SQLite.
> I have copied all collection folders from the Linux PC to the Mac and used Tools->Maintenance-> Sync Metadata and Database on the Mac to try to rebuild the database (now SQLite) from the metadata in the photo and XMP files. As far as I can tell most data has been recreated except for the group definitions (I have lots of groups for JPG-RAW combinations, panorama photos, time series etc.)
> My questions:
> - Can the group definitions be recovered from the Linux PC and added to the Mac?
> - Are there other relevant features besides the group definitions that may not have been recreated from the metadata in the files?
> - Was this a proper way to transfer everything from the Linux PC to the Mac or should I have used another method?
>