[Digikam-devel] [digikam] [Bug 325653] New: database migration is very slow

[Thomas Bleher]

https://bugs.kde.org/show_bug.cgi?id=325653

            Bug ID: 325653
           Summary: database migration is very slow
    Classification: Unclassified
           Product: digikam
           Version: 3.3.0
          Platform: unspecified
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: Database
          Assignee: digikam-devel at kde.org
          Reporter: ThomasBleher at gmx.de

I recently wanted to migrate my digikam database from MySQL to SQLite. However,
the database migration is extremely slow. top(1) reported that the digikam
process consumed more than 1700 minutes for the migration. At 90,000 pictures,
that is more than one second per picture! The resulting database is 150MB
large, so this is a throughput of 1.5kB/s. This is on a two-core Intel Celeron
CPU 847 @ 1.10GHz with 4GB of RAM and a local MySQL database.
Clearly this could be optimized a lot. A mysqldump of the original database
finishes in less than 8 seconds!

Peeking at the process with a debugger, it seems that most of the time is spent
in the Qt event loop. Maybe the progress bar is repainted for every row in the
database?

Reproducible: Always

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