[Digikam-users] Long database sync

[Gilles Caulier]

This is a copy of private mail from another developer who have tried
to reproduce the problem :

>The metadatasynchronizer processed TAlbums correctly. I have moved to test my
>DB on the SSD. My about 20000 images then require approximately 6 minutes. One
>should of course not select tags, because otherwise will double synronisiert.

Gilles Caulier

2015-05-13 20:07 GMT+02:00 Gilles Caulier <caulier.gilles at gmail.com>:
> 2015-05-13 19:18 GMT+02:00 Noeck <noeck.marburg at gmx.de>:
>> Hi Gilles,
>>
>> thanks for your reply and for confirming my guesses. Please find answers
>> to your questions inline.
>>
>>>> I chose "From image metadata to database" and not
>>>> "From database to image metadata", so according to my understanding,
>>>> only the database changes. And indeed the image files were not modified
>>>> (according to the file system).
>>>
>>> yes exactly, but... image metadata must be read to re-populate DB.
>>> It's delegate to Exiv2 shared library.
>>
>> Ok. But read not written and the system monitor showed it as written.
>>
>>>> In the end, the mentioned database sync took 25h with a constant write
>>>> rate of 12 - 15 MB/s. Which naively calculated sums up to 1.2 TB (!).
>>>
>>> I don't understand this value. Are you sure that 15 MB/s is for
>>> writing and not reading ?
>>
>> Yes. This is what astonishes me.
>>
>>>> What puzzles me is that the sum of all images is only 200 GB (50k files)
>>>> so much less than the data written to disk.
>>>
>>> Possible problem can be relevant of a bug about wrong albums list
>>> passed to maintenance tools, discovered recently and fixed in 4.10.0
>>>
>>> Q : did you use multicore option in Maintenance dialog ?
>>
>> No this was done without the multicore option. So there might be some
>> gain here. However it seems pretty much i/o bound.
>>
>> And I chose all albums and all tags (no selection here). I was wondering
>> if that scans all files twice?
>
> yes, i suspect this. Look this entry in bugzilla :
>
> https://bugs.kde.org/show_bug.cgi?id=342791
>
> This affect Thumbnail Generator, Quality Sorter, and Fingerprints Generator.
>
> We must take a look if other maintenance tools are affected (in your
> case DB synchronizer).
>
> Gilles Caulier