[digikam] [Bug 373003] New: wrongly calculated uniqueHash

[Kusi]

https://bugs.kde.org/show_bug.cgi?id=373003

            Bug ID: 373003
           Summary: wrongly calculated uniqueHash
           Product: digikam
           Version: 5.2.0
          Platform: openSUSE RPMs
                OS: Linux
            Status: UNCONFIRMED
          Severity: major
          Priority: NOR
         Component: Database-Mysql
          Assignee: digikam-devel at kde.org
          Reporter: kusi at forum.titlis.org
  Target Milestone: ---

A new uniqueHash algorithm was implemented a few years ago. See
https://bugs.kde.org/show_bug.cgi?id=210353. The new algorithm in uniqueHashV2
was only made available for newly created databases. An already existing
database was (and is till today) still using the old uniqueHash algorithm. My
10 years old digikam db still uses the old uniqueHash algo. The old algo worked
fine till digikam 4.14. During the porting to DK 5, a bug was introduced for
the old algo:

In dimgloaded.cpp, the KDE4 command for the old v1 uniqueHash algo

   KMD5 md5;
   ...
   hash = md5.hexDigest();

was replaced in the KDE5 porting with ( still uniqueHash v1)

   QCryptographicHash md5(QCryptographicHash::Md5);
   ...
   hash = md5.result();

which is wrong. Instead, it should have been replaced by

   QCryptographicHash md5(QCryptographicHash::Md5);
   ...
   hash = md5.result().toHex();

See the migration document
https://api.kde.org/frameworks/kdelibs4support/html/classKMD5.html#a49b31c3e5eb180fa8be8c8f576266221

As a consequence, a database created before 2010 calculates different
uniqueHash values in DK5 compared to DK4. Furthermore, UTF8 cannot be used
since some of the now calculated uniqueHash values are not valid UTF8
characters, the SQL server erorrs with

  "REPLACE INTO Images  ( album, name, status, category, modificationDate,
  fileSize, uniqueHash )  VALUES (?,?,?,?,?,?,?);"
  Error messages: "QMYSQL3: Unable to execute statement" "Incorrect string
  value: '\\xF1\\x9E\\xA6\\x87' for column 'uniqueHash' at row 1" 1366 2
  Bound values:  (QVariant(int, 118053), QVariant(QString, "P4240656.JPG"),
  QVariant(int, 1), QVariant(int, 1), QVariant(QString,
  "2016-10-30T19:16:42"), QVariant(qlonglong, 6951936), QVariant(QString,
  "m�7�\U0005E987"))

There is uniqueHashVersion in the System table, but the value "2" in DK4 and
DK5 return different hash values.

The fix would be easy, just add the missing ".toHex()". However, all images
added in DK5 already contain the invalid hash values. They need legacy
treatment.

The most clean solution is to get rid of hashValue version 1 and recalculate
all hash values in the next DK release

As as sidenote: hashValueV2 is not affected by this bug. This means a db
created after 2010 is not affected

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