Digikam database

20160130 jean AT huens.be

intro

Distributor ID:	Ubuntu
Description:	Ubuntu 14.04.3 LTS
Release:	14.04
Codename:	trusty


digikam             4:4.14.0-trusty~ppa1               amd64

DB Organisation:

The digikam database is sqlite format.
It contains a table AlbumRoots used to locate de database(s) and pictures;

On a correctly working system it looks like:

$ sqlite3 ~/Pictures/digikam4.db 
SQLite version 3.8.2 2013-12-06 14:53:30
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> .tables
AlbumRoots          ImageHistory        ImageTagProperties  Tags              
Albums              ImageInformation    ImageTags           TagsTree          
DownloadHistory     ImageMetadata       Images              VideoMetadata     
ImageComments       ImagePositions      Searches          
ImageCopyright      ImageProperties     Settings          
ImageHaarMatrix     ImageRelations      TagProperties     
sqlite> .schema AlbumRoots
CREATE TABLE AlbumRoots
                            (id INTEGER PRIMARY KEY,
                            label TEXT,
                            status INTEGER NOT NULL,
                            type INTEGER NOT NULL,
                            identifier TEXT,
                            specificPath TEXT,
                            UNIQUE(identifier, specificPath));
CREATE TRIGGER delete_albumroot DELETE ON AlbumRoots
                BEGIN
                DELETE FROM Albums
                WHERE Albums.albumRoot = OLD.id;
                END;
sqlite> select * from AlbumRoots;
1||0|1|volumeid:?uuid=1a87f605-16e3-46f2-b973-37fe2b414561|/home/lucienne/Pictures
sqlite>

One (as root) can look at the devices and its UUID:

# lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   1.8T  0 disk 
├─sda1   8:1    0 145.1G  0 part /
├─sda2   8:2    0     1K  0 part 
├─sda5   8:5    0   8.8G  0 part [SWAP]
└─sda6   8:6    0   1.7T  0 part /home/lucienne
sr0     11:0    1  1024M  0 rom  

# blkid
/dev/sda1: UUID="1a87f605-16e3-46f2-b973-37fe2b414561" TYPE="ext4" 
/dev/sda5: UUID="a605a0e2-f440-407c-8de3-7872b366a8d1" TYPE="swap" 
/dev/sda6: UUID="a343aead-ce3b-431e-8b49-da2a358c3a9b" TYPE="ext4"

The (for me) amazing point is that the UUID of the / partition  (/dev/sda1) is combined with a Path /home/lucienne/Pictures
which is on the /sda6 partition...

Cause of database corruption.

When switching to a new machine  using a backup of the digikam files, we did encounter two problems:

1) The disks UUID's did change.
2) The location of the Picture files and Digikam DB got changed.

This seems related to

Bug 175923 - digikam uses wrong album root path/wrong disk uuid 


$ sqlite3 ~/Backup_digikam/digikam4.db.2015120323
SQLite version 3.8.2 2013-12-06 14:53:30
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> select * from AlbumRoots;
1||0|1|volumeid:?uuid=7199951a-fea7-4d70-ad7d-6dbeff318ee5|/lucienne/Pictures

At startup digikam produces a screen :
startup message

This is rather confusing, moreover digikam seems to work at the first but some features are missing
(e.g.  comments added tot pictures,  print assistant, ....0

Workaround

  1. make a backup of your digikam4.db
  2. when digikam is not running, use sqlite3 to edit correct the AlbumRoots table :
    $ sqlite3 digikam4.db
    ...
    sqlite> select * from AlbumRoots;
    1||0|1|volumeid:?uuid=7199951a-fea7-4d70-ad7d-6dbeff318ee5|/lucienne/Pictures
    sqlite> UPDATE AlbumRoots SET specificPath='/home/lucienne/Pictures' where specificPath='/lucienne/Pictures';
    sqlite> select * from AlbumRoots;
    1||0|1|volumeid:?uuid=7199951a-fea7-4d70-ad7d-6dbeff318ee5|/home/lucienne/Pictures
    sqlite> .exit
  3. Start digikam. Now it will detect the UUID is not correct, but /home/lucienne/Pictures exits.
    And it suggests to correct this problem.
    Start_with_correct_path
  4. Digikam can cope with changing UUIDs but only if the location of the database/albums  remains correct.

  5. If you prefer to edit UUID in sql take into account that special chars in the string must be escaped by  single quotes :
    sqlite> UPDATE AlbumRoots SET identifier='?uuid=8c178eec-e410-4346-85c1-0fe9db3336f9' WHERE identifier='?uuid=8c178eec-e410-4346-85c1-0fe9db3336f8';