SQL with WebAssembly

[Infinity]

I would like to compile my application for WebAssembly. The animatedtiles example as described in this article https://blog.qt.io/blog/2019/03/05/using-docker-test-qt-webassembly/ works without any problems. In my application I use the sql module. If I want to compile it I get the following error:

Info: creating stash file /project/build/.qmake.stash
cd address/ && ( test -e Makefile || /usr/local/Qt-5.13.1/bin/qmake -o Makefile /project/source/address/address.pro ) && make -f Makefile 
cd user/ && ( test -e Makefile || /usr/local/Qt-5.13.1/bin/qmake -o Makefile /project/source/user/user.pro ) && make -f Makefile 
cd login/ && ( test -e Makefile || /usr/local/Qt-5.13.1/bin/qmake -o Makefile /project/source/login/login.pro ) && make -f Makefile 
Project ERROR: Unknown module(s) in QT: sql
Makefile:50: recipe for target 'sub-address-make_first' failed
make: *** [sub-address-make_first] Error 3
make: *** Waiting for unfinished jobs....
Project ERROR: Unknown module(s) in QT: sql
Project ERROR: Unknown module(s) in QT: sql
Makefile:152: recipe for target 'sub-user-make_first' failed
Makefile:127: recipe for target 'sub-login-make_first' failed
make: *** [sub-user-make_first] Error 3
make: *** [sub-login-make_first] Error 3

Why is the sql module not found?

[SGaist]

Hi,

AFAIK, the QtSql module is currently not available for web assembly.

@lorn-potter might be able to shed some more light on it.

[JonB]

@infinity , @SGaist
I asked this recently See the response I got at https://forum.qt.io/topic/105944/qt-for-webassembly-widget-example-gone/18

1.I understand about limitations like no local files, no sub-processes. What about MySQL database access via the Qt classes? Do I assume you cannot have your code access SQL db from browser?

Not at this point. Although someone has now ported sqlite to wasm, which would be the first step.

[lorn.potter]

Someone has ported sqlite to wasm...
https://github.com/fluencelabs/sqlite

You could start with that.
I am unclear if any work on the Qt side would be needed to get Qt compiled with support for sqlite.

[Libra]

@Infinity Hi, Did you get any solution of this Qt module not found issue while building webassembly project

[Infinity]

No. I switched from MySQL to SQLite.

[8Observer8]

@SGaist said in SQL with WebAssembly:

AFAIK, the QtSql module is currently not available for web assembly.

I don't understand why is there no the Qt SQL module in this list: https://doc.qt.io/qt-6/wasm.html#supported-qt-modules

Because QSLite really works on WebAssembly. I ran the next code:

#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlError>
#include <QtSql/QSqlQuery>
#include <QtSql/QSqlRecord>
#include "widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
    db.setDatabaseName("users.sqlite");
    db.open();
    qDebug() << db.isOpen();
    QSqlQuery query;
    qDebug() << query.exec("create table users_table (id int primary key, nickname varchar(50), score int)");
    qDebug() << query.lastError();
    qDebug() << query.exec("insert into users_table values(0, 'John', 5);");
    qDebug() << query.lastError();
    QSqlQuery selectQuery("select * from users_table");
    int idName = selectQuery.record().indexOf("nickname");
    qDebug() << idName;
    while (selectQuery.next())
    {
        QString name = selectQuery.value(idName).toString();
        qDebug() << name;
    }
    db.close();
}

It works on WebAssembly:

[SGaist]

@8Observer8 that's only speculation but it might be:

• Because only SQLite is a supported backend and thus claiming that the module itself is supported is misleading
• Because the addition is fairly recent and the documentation has not been update
• Might be still a tech preview

And a flurry of other reasons but again these are speculations.

[Christian Ehrlicher]

@SGaist and a forth point from the Maintainer Perspective - it was not yet tested because afaik Sqlite gained this feature only recently and we had not yet time to test it esp. since Web Assembly is low priority to me 🙂
So it can be said it's working by accident. 😉