digiKam - understanding duplicates search restrict to reference album

[scottdk]

I have been doing some experiements to try to understand how the logic behind the Restriction field works when searching for duplicates.

The options are:
*None
*Restrict to reference album
*Exclude reference album.

"None" returns the same result as "Exclude reference album"
"Restrict to reference album" returns no results.

How do these settings actually work?


My test data is set up as follows, where all the photos are copies of the same file.


Albums
├── folder-A
│   ├── subfolder-A1
│   │   └── Photo-A1.JPG
│   └── subfolder-A2
│       └── Photo-A2.JPG
└── folder-B
    ├── subfolder-B1
    │   └── Photo-B1.JPG
    └── subfolder-B2
        └── Photo-B2.JPG

subfolder-A1 is set as the reference (Prefer selected folder as reference)

Test 1 - Restriction: None
Four duplicates returned. Reference image is Photo-A1




Test 2 - Restriction: Restrict to Reference Album
No duplicates returned.




Test 3 - Restriction: Exclude Reference Album
Four duplicates returned. Reference image is Photo-A1.



I'm not trying to acheive a specific outcome. I just want to understand how all the options work so I can find creative ways to use the tools to help remove duplicates from 193,000 photos collected over 22 years in a number of backups duplicated across iPhoto, Google Photos, or simply saved to folders, all of which have altered the image filesize and dates slightly. To complicate matters, thanks to camera upgrades, the exact same filename can be used for different photos taken years apart. (Thankfully the EXIF datetaken is intact in most cases). I expect that more than 90% are duplicates.