Re: [Interest] Close DB connection when not actively using?

[Roland Hughes]

You opened the database in main. The function you called is so small it most likely was placed in-line by the compiler. This would be especially true if you did nothing with dbOpen. You have no reason to open it there. Again, read the fine manual. http://doc.qt.io/qt-5/qsqldatabase.html#database Every time you call QSqlDatabase::database( "someConnectionName") it will open the database if it is not currently open. You should never open the database in main. Just set up all of the values for it. On 08/21/2018 03:54 PM, Israel Brewster wrote: Ok, maybe you can give me a pointer on what I'm doing wrong then. My code is structured like the following: bool openDatabase(){ QSqlDatabase db=QSqlDatabase::addDatabase('QSQLITE'); db.setDatabaseName(<path_to_my_database_file>); return db.open(); }  int main(int argc, char *argv[]) { QApplication a(argc, argv); ... <various initialization code> ... bool dbOpen=openDatabase(); ... <more initilization> return a.exec(); } And if I put a breakpoint at any point after the call to OpenDatabase, the database is open - it does not close, even though that QSqlDatabase object went out of scope. At no point in my application do I keep a copy of QSqlDatabase around in any of my classes - every call to QSqlDatabase is as a function local member, and as such goes out of scope (thereby theoretically calling the destructor) as soon as the function exits.  So what am I missing here?  ----------------------------------------------- Israel Brewster Systems Analyst II 5245 Airport Industrial Rd Fairbanks, AK 99709 (907) 450-7293 -----------------------------------------------       On Aug 21, 2018, at 12:31 PM, Roland Hughes <rol...@logikalsolutions.com> wrote: Why are you creating yet another class instead of properly structuring your application? Take a gander at http://www.logikalsolutions.com/wordpress/information-technology/qt-and-usb-pt-4/ for some ideas. You probably also want to find a copy of this book http://www.theminimumyouneedtoknow.com/qt_book.html Most importantly you need to read the fine manual. http://doc.qt.io/qt-5/qsqldatabase.html#dtor.QSqlDatabase QSqlDatabase::~QSqlDatabase() Destroys the object and frees any allocated resources. Note: When the last connection is destroyed, the destructor implicitly calls close() to release the database connection. See also close(). If your database is open for the life of the application then the application has a failed architecture. Database connections aren't supposed to have actual life spans. On 08/21/2018 03:08 PM, Israel Brewster wrote: Ideally, what I'd have is a system where you set up the connection, and then it automatically opens/closes the connection when needed (i.e. when doing a SELECT, INSERT, UPDATE, etc). With my app, this would generally only be for a) periodic updates or b) in direct response to user input, so most of the time the connection could remain closed. To the best of my knowledge (correct me if I am wrong), this is not possible with the existing QSqlDatabase/ QSQLITE database driver classes. -- Roland Hughes, President Logikal Solutions (630) 205-1593 http://www.theminimumyouneedtoknow.com http://www.infiniteexposure.net http://www.johnsmith-book.com http://www.logikalblog.com http://www.interestingauthors.com/blog http://lesedi.us _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest -- Roland Hughes, President Logikal Solutions (630) 205-1593 http://www.theminimumyouneedtoknow.com http://www.infiniteexposure.net http://www.johnsmith-book.com http://www.logikalblog.com http://www.interestingauthors.com/blog http://lesedi.us

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