Add in JSON Array

[sneubert]

Hi @Mikeeeeee,

please provide some more information. Do you use QJsonDocument or javascript JSON in qml? Can you provide a minimal example?

[Mikeeeeee]

Yes, I use QJsonDocument. There is only one array in json file. There is QString LastResume in my project. I would like to add LastResume in the array in json file. But json file may be is large. That's why I don't want load the whole file.

[sneubert]

Since JSON is a text file, you maybe faster in creating two QTextStream, one for reading your JSON file, and one for writing to a new file. You can process the input file line by line until you hit the array end character ], where you can insert your string. This is kind of change by copy. But I don´t know if this is really faster, you have to try.

Maybe someone else here has experience in modifying large files. Maybe this can be faster with memory mapping the file?

[mrjj]

Hi
What Qt version are you using ?
The array must be ULTRA huge for it to take time.
https://bugreports.qt.io/browse/QTBUG-44737

so i wonder if its older Qt version.

[Mikeeeeee]

My version 5.11.2

json file can occupy several gigabytes

[jsulm]

@Mikeeeeee said in Add in JSON Array:

json file can occupy several gigabytes

!
Wondering what the use case for such huge JSON file is...

[Mikeeeeee]

I predicted to use it for saving array. But I desided to use SQL.

[mrjj]

@Mikeeeeee
Using SQL is way better as a JSON file this size will consume TONS of memory with a DOM parser like QJsonDocument.

[Christian Ehrlicher]

QJson also has an internal memory limit which is imo below 1GB. There was a thread about this on the mailing list some months ago (during the cbor introduction iirc)

[sierdzio]

@Christian-Ehrlicher said in Add in JSON Array:

QJson also has an internal memory limit which is imo below 1GB. There was a thread about this on the mailing list some months ago (during the cbor introduction iirc)

That limit (128 MB) is for saving to binary JSON only, if I recall correctly.