QSqlDatabase 数据库操作没有removeDatabase 导致程序崩溃(此文极有可能是错误的，仅作个人留档参考)

最新推荐文章于 2023-11-27 09:33:15 发布

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最新推荐文章于 2023-11-27 09:33:15 发布 · 4.7k 阅读

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#数据库 #database #query #leak #output #function

本文探讨了QSqlDatabase在使用后未正确移除导致的资源泄漏问题，指出在存在活跃查询时调用removeDatabase将引发警告。正确的做法是确保查询结束后数据库连接超出作用域自动关闭，然后安全地移除数据库连接。调试中遇到的问题是尝试关闭已使用的'qt_sql_default_connection'导致的崩溃。

void QSqlDatabase::removeDatabase ( const QString & connectionName ) [static] Removes the database connection connectionName from the list of database connections. Warning: There should be no open queries on the database connection when this function is called, otherwise a resource leak will occur. Example: // WRONG QSqlDatabase db = QSqlDatabase::database("sales"); QSqlQuery query("SELECT NAME, DOB FROM EMPLOYEES", db); QSqlDatabase::removeDatabase("sales"); // will output a warning // "db" is now a dangling invalid database connection, // "query" contains an invalid result set The correct way to do it: { QSqlDatabase db = QSqlDatabase::database("sales"); QSqlQuery query("SELECT NAME, DOB FROM EMPLOYEES", db); } // Both "db" and "query" are destroyed because they are out of scope QSqlDatabase::removeDatabase("sales"); // correct To remove the default connection, which may have been created wi