When performing color autocorrection in BQM there seems like long freezes of GUI(especially visible if used on all cores and on other directory to output). Even after all new photos already created, it takes great amount of time to GuI to unfreeze and catch up with all operations. Futhermore if you minimize and then restore QBM or Digikam windows when this operations performed - they would be black(wouldn't draw Interface) for minute or two.

When running in gdb there seems numerous strings like:
digikam(9707)/digikam (core) Digikam::DatabaseCoreBackendPrivate::checkRetrySQLiteLockError: Detected locked database file. There is an active transaction. Waited but giving up now. 
digikam(9707)/digikam (core) Digikam::ImageInfo::fromLocationAlbumAndName: No itemShortInfo could be retrieved from the database for image "DSC_1626.JPG"

Reproducible: Always

Steps to Reproduce:
1. Choose ~200 photo(I used jpeg) in album
2. Click BQM and choose color autocorrection
3. Click Run

Actual Results:  
GUI freezes for long time and almost not respond.
If window minimized and restored there would be no GUI draw for long time(black window).
Program would be unusable for next 15 minutes even if all new files already compiled in first two minutes.

Expected Results:  
GUI shouldn't be freezed for such long time and of course there shouldn't be any problem to draw GUI if window was restored.

KDE Platform Version: 4.14.6
Qt Version: 4.8.6
Operating System: Linux 3.16.7-7-desktop x86_64
Distribution: "openSUSE 13.2 (Harlequin) (x86_64)"

System FS - BTRFS.
Databases of digikam located on /home (FS - XFS)

Processor: i7 2600k
RAM: 8GB
HDD