No result in QTSql query

I've created a function to exeute a query to postgresql database. I call the function with the query string, a boolean in order to tell me if the query is ok or not and an error string. If I try with a correct query (tested in postgresql prompt) I dont enter in xQueryResult.next() loop but xQueryResult is not empty. I use c++17, postgresql database and QTSql library (Qt 5.15)

#include "SqlDatabase.h"
#include <QtSql\QSqlError>
#include <QtSql\QSqlQuery>
#include <QtSql/QSqlRecord>
#include <QJsonObject>
#include <QJsonArray>


QJsonDocument SqlDatabase::fun(const QString &i_xQuery, bool& bOk, QString& strErrorMessage)
{
    QJsonDocument xJsonDoc;
    QSqlQuery xQueryResult = m_pxCurrentDatabase->exec(i_xQuery);

    if (QSqlError::NoError != xQueryResult.lastError().type())
    {
        bOk = false;
        strErrorMessage = QString("%1: %2").arg(__FUNCTION__).arg(xQueryResult.lastError().text());
        return xJsonDoc;
    }

    QJsonArray xRecordsArray;
    int iFieldIndex = 0;
    int iFieldCount = 0;
    xQueryResult.first();
    while (true == xQueryResult.next())
    {
        const QSqlRecord& xSqlRecord = xQueryResult.record();
        QJsonObject xJsonObj;

        if (iFieldCount == 0)
            iFieldCount = xSqlRecord.count();

        for (iFieldIndex = 0; iFieldIndex < iFieldCount; iFieldIndex++)
        {
            QString strKey = xSqlRecord.fieldName(iFieldIndex);
            xJsonObj[strKey] = QJsonValue::fromVariant(xSqlRecord.value(iFieldIndex));
        }

        xRecordsArray.append(xJsonObj);
    }

    QJsonObject xObject;
    xObject["Records"] = xRecordsArray;
    xObject["NumRowsAffected"] = xQueryResult.numRowsAffected();
    xObject["LastInsertId"] = xQueryResult.lastInsertId().toString();
    xJsonDoc.setObject(xObject);

    bOk = true;
    strErrorMessage = "";
    return xJsonDoc;
}

i call the function from main with

 QJsonDocument xResultDoc;
 std::unique_ptr<Exercise::Comm::SqlDatabase> m_pxDatabase;
QString strQuery = "INSERT INTO public.tab1 (id,name_id,descr_id,description,"user") 
VALUES (
'test',
'$Default',
0,
'test',
''
)RETURNING id;"
  bool bOk;
  QString strErrorMessage;
xResultDoc = m_pxDatabase->exec2(strQuery, bOk, strErrorMessage);