Question

I am using QT, on a Windows 10 box. I am connecting to a MS_SQL server to pull records so that I can relocate them in a Postgres database.

I'm using the QSqlDatabase class then an QSqlQuery to pull rows. This is shockingly slow ~2 rows / second. I was expecting performance maybe 500 times faster than this. Is this the sort of performance I have to deal with, or am I missing something?

Here is a simplified version of what I'm trying to do. This performs at about 2Hz.

int main(int argc, char *argv[])
{
    QSqlDatabase db = QSqlDatabase::addDatabase("QODBC3");
    db.setDatabaseName("DRIVER={SQL Server};Server=10.10.1.32;Database=[DB_NAME];Uid=[UID];pwd=[PWD]");

    if (!db.open()) return -1;

    QSqlQuery query;
    bool worked = query.exec("select * from [TABLE_NAME]");
    if (!worked) return -2;

    while(query.next())
    {
        QSqlRecord record = query.record();
        for(int i = 0; i < query.record().count(); i++)
        {
            QVariant value = record.value(i);
            fprintf(stdout, "%s\t",qPrintable(value.toString()));
        }
        fprintf(stdout, "\n");
    }
}

Answer 1

好吧，我的一个伙伴弄清楚了事情。事实证明，QQuery的默认设置是使用双向游标-至少与ODBC驱动程序一起使用。

QQuery具有属性“ forwardOnly”。将其设置为true，虽然代码不会加快500倍（就像我期望的那样），但确实可以加快250倍。是的，一点都不夸张。

这是上面示例的mod。

QSqlQuery query;
query.setForwardOnly(true);
bool worked = query.exec("select * from [TABLE_NAME]");

QT QSqlDatabase connected to MSSql pulls rows EXTREMELY slowly

1 个答案: