Is there any Qt SQLite plugin for storing database in RAM by VFS (for loading database from Qt resource file)?

Question

I have some :/test.sqlite3 database inside .qrc. And the goal is to directly use this database in program. Database used only for reading.

QSqlDatabase::setDatabase(":/test.sqlite3") not works, because Qt SQLite not designed for working with Qt's filesystem.

One of solutions is copying database from .qrc into D:\temdb.sqlite3 and using it by QSqlDatabase::setDatabase("D:\\temdb.sqlite3"). But program must not work with OS filesystem.

Second solution is storing :/dump.sql in resources, then creating in-memory database by QSqlDatabase::setDatabase(":memory:") and importing dump into it by reading and executing lines from :/dump.sql. But this method is slow.

And, finally, hard but true way is creating own Qt plugin for SQLite with VFS implementation for reading database from RAM, where we have bytes of ":/test.sqlite3".

Is there any another easy way?

P.S. I have already read all questions like Converting in-memory sqlite database to blob/char array and other, so don't mark it as duplicate. My question is about any other methods.

Answer 1

You could take advantage of Qt QTemporaryFile to copy your data and start. QTemporaryfile works on every os.

Here is an example (this temporary file is associated to the entire qApp so that it will be removed once you quit the application):

QTemporaryFile tmpFile(qApp);
tmpFile.setFileTemplate("XXXXXX.sqlite3");
if (tmpFile.open()) {
    QString tmp_filename=tmpFile.fileName();
    qDebug() << "temporary" << tmp_filename;

    QFile file(":/test.sqlite3");
    if (file.open(QIODevice::ReadOnly)) {
        tmpFile.write(file.readAll());
    }

    tmpFile.close();
}

The you can reopen the file tmpFile.fileName() as QSqlDatabase:

QSqlDatabase::setDatabase(tmpFile.fileName());