[Digikam-users] solving lost tag problem

[Simon Oosthoek]

Hi all (and Gilles)

I notice a recurring problem on the mailinglist regarding lost tags. 
AFAICT this happens often to people who change their disk for a 
collection or some other problem where the digikam database loses sync 
with the actual image store. I ran into this once (or more than once) 
and reported my issues here: https://bugs.kde.org/show_bug.cgi?id=215486

Wouldn't this be easily solvable using a small problem solving feature? 
(this could lead to a feature request later on ;-)

I hope I'm correct in describing the tagging system in the database as:
* there's a table with images
* there's a table with tags (hierarchy is represented by a column parent 
id(pid))
* a table imagetags which links images to tags.

When a database is lost or "unlinked" from the images, a new database 
can be created but then the imagetags table is recreated without the 
tags (unless the tags are inside the image's exif).

If an old database is available, it should have a table images with the 
above mentioned tables and in the images table is a unique hash value 
for each image.
Am I right to assume that this hash value is easy to recalculate and can 
be used to track down old image-tag relationships?
If so, this could be used to connect the new database with the old 
database and thus restore old tags and their links to images.

Combined with a supportive GUI, this would solve a lot of issues I 
think. Any comments?

/Simon