Adding QJsonObject to QJsonDocument takes a lot of time

MrHandSOme

QJsonObject rootObj;
rootObj["a1"]=a1obj;
rootObj["a2"]=a2obj;
rootObj["a3"]=a3obj;
rootObj["a4"]=a4obj;
rootObj["a5"]=a5obj;

QJsonDocument newDocument(rootObj);

This part of my code creates a lot of delay in the application. It takes approximately 100 ms. How do I speed this up?

SGaist

Hi,

What are all these objects ?
How did you measure the time ?
Are you using a debug build ?
On which OS are you seeing that ?
Which version of Qt are you using ?

MrHandSOme

@SGaist
All objects are QString.
I calculate by putting qtime in the upper and lower parts. Even if I don't do this, it creates a slowness in the interface anyway.
No i am using release build.
Windows 10.
6.6.0.
Thank you.

Paul Colby

Hi @MrHandSOme,

I calculate by putting qtime in the upper and lower parts.

QTime has some overhead (probably very little, but still...). For interest, try this:

    const quint64 start = QDateTime::currentMSecsSinceEpoch();
    QJsonObject rootObj; qDebug() << (QDateTime::currentMSecsSinceEpoch()-start) << "rootObj";
    rootObj[QStringLiteral("a1")]=QStringLiteral("a1obj"); qDebug() << (QDateTime::currentMSecsSinceEpoch()-start) << "a1obj";
    rootObj[QStringLiteral("a2")]=QStringLiteral("a2obj"); qDebug() << (QDateTime::currentMSecsSinceEpoch()-start) << "a2obj";
    rootObj[QStringLiteral("a3")]=QStringLiteral("a3obj"); qDebug() << (QDateTime::currentMSecsSinceEpoch()-start) << "a3obj";
    rootObj[QStringLiteral("a4")]=QStringLiteral("a4obj"); qDebug() << (QDateTime::currentMSecsSinceEpoch()-start) << "a4obj";
    rootObj[QStringLiteral("a5")]=QStringLiteral("a5obj"); qDebug() << (QDateTime::currentMSecsSinceEpoch()-start) << "a5obj";
    QJsonDocument newDocument(rootObj); qDebug() << (QDateTime::currentMSecsSinceEpoch()-start) << "newDocument";

For me (on Linux though, I don't have Windows handy just at the moment), it shows all of that code executing within a single millisecond, as expected. My output:

0 rootObj
1 a1obj
1 a2obj
1 a3obj
1 a4obj
1 a5obj
1 newDocument

If that code is slow for you, show us the output. If it's not slow, then try replacing the various QStringLiteral()'s with your versions one at a time and see if that reveals anything.

Cheers.