[KPhotoAlbum] Recalc checksum upon image modification?

[Jan Kundrát]

Tim McCormack wrote:
> I was under the impression that KPA would recalculate the checksum of 
> any image in the collection that had been modified since last DB save.

Hi Tim,
we don't check file checksums at startup as it's really very expensive 
operation. My pretty small DB has about 16k images and takes 32GB on 
disk. My laptop can process up to 300MB/s of data per one core when 
computing the MD5 and being fed by 8k blocks (`openssl speed md5`). I 
guess that Qt's implementation is not as optimized as that in OpenSSL, 
but even if it was, it would take more than two minutes of CPU time on 
each startup of KPA. When using both cores and clever tricks, I could 
get at one minute if I were lucky and filesystem/disk was fast. But as 
my laptop is one year old, so it would take about twenty minutes (!) 
just to read the data from disk. We have plenty of users on older 
machines and/or with images stored on a network disk over 100MBps or 
slower ethernet (and for some users, even just reading the directory 
list and calling stat() on each file was a killer), so enabling this 
globally is not really an option.

> I've discovered that this is not true. Is there any way of forcing KPA 
> to do this?

Sure, Maintenance -> Recalculate Checksum does that.

> At the very least, the checksum should be updated in index.xml whenever 
> one of the plugins is applied to the image.

Good point, please add this as a wish to our bugzilla (bug.kde.org).

Cheers,
-jkt

-- 
cd /local/pub && more beer > /dev/mouth

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