[Digikam-devel] [digikam] [Bug 331742] New: BQM takes a lot of time processing >200 images

[regi.hops at gmx.net]

https://bugs.kde.org/show_bug.cgi?id=331742

            Bug ID: 331742
           Summary: BQM takes a lot of time processing >200 images
    Classification: Unclassified
           Product: digikam
           Version: 3.5.0
          Platform: openSUSE RPMs
                OS: Linux
            Status: UNCONFIRMED
          Severity: crash
          Priority: NOR
         Component: Batch Queue Manager
          Assignee: digikam-devel at kde.org
          Reporter: regi.hops at gmx.net

openSUSE x86_64 / KDE4.12.2

In an album with around 1000 images I selected 410 images (jpeg) through the
search, then place them in the BQM.
Selecting the rescaling tool and start the batch process.
Output goes to a new album.
Original size was around 5000px width and I selected to reduce size to 1920px
width.
The process of rescaling itself was done in approx. 2 Minutes, but after than I
recognized a lot of SQL activity which took around 30 minutes.
So all in all the whole process of rescaling took > 30 minutes, while
throughout this time digiKam wasn't responding in any way.

Attached is an image that shows the CPU-Usage during this process.
Visibly it divides in 4 blocks:
First high CPU-Usage - images are rescale, after that all new images are
physically there.
Second block of low CPU-Usage - some SQL-Activity
Third block of intermittent CPU-Usage - lots of (re)reads to the newly created
files and lots of SQL-Activity.
Forth block of constant CPU-Usage - moderate (re)reads to the newly created
files and moderate SQL-Activity to the thumbnail-DB.



Reproducible: Always

Steps to Reproduce:
1. Select >200 (in my case 410) images for batch processing
2. Output goes to a new album
3. Selected tool rescale with 1920px
Actual Results:  
Process takes much too long, digiKam is not responding during batch process

Expected Results:  
Process should be much faster (and in the past 2.x version it was)

Due to not responding for over 30 minutes the user must think the process is
crashed or hangs.

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