how toconvert sqlite3 database file to .csv file in qt code ?

VRonin

@sksh said in how toconvert sqlite3 database file to .csv file in qt code ?:

it take to much time to generate .csv file

Can you show us your code?

JonB

@sksh
Is it the actual time to output the CSV file, or is it just the time to iterate over 20,000 rows of 30 columns? You could probably optimize @SGaist's algorithm to output to file as you go along rather than build in-memory string lists + join, but that may be marginal. Do give us some idea of your "it take to much time", seconds/minutes/what?

sksh

@JonB it is take more then 30 second for only 1000 entry

Christian Ehrlicher

You should show us your code - I don't think reading some lines and writing them out into a file will take that long when properly coded...

sksh

Thank you for your replay

I seen my code and i found that it is not stop read some data constant.so please have any solution for it?
my code as below:

int s;
Application conn;

QSqlQuery* query= new QSqlQuery(conn.mydb);

query->prepare(" select * from teb1;");
QVector<QStringList> lst;

  while (query->exec())
  {
        QSqlRecord record = query->record();
        qDebug()<<"record"<<record;
        QStringList tmp;
        for(int i=0;record.value(i)=="\0";i++)//record.count()
        {
            tmp<<record.value(i).toString();
        }
        lst.append(tmp);
        qDebug()<<"tmp"<<s++<<"data"<<tmp;
  }
  foreach(const QStringList &var,lst)
  {
      qDebug()<<"sadsfsfsd"<<var;
  }

SGaist

Several things:

No need to allocate query on the heap (furthermore, you don't delete it so you have a memory leak)
Why put the exec call in a while loop ? It's the next call you need to do that for.
Why build that huge QStringList ? Just dump your table line by line directly into the file. That will save time and memory.

sksh

@SGaist Thanks sir
can you share me a sample code for this?

VRonin

QString escapedCSV(QString unexc)
{
    if (!unexc.contains(QLatin1Char(',')))
        return unexc;
    return '\"' + unexc.replace(QLatin1Char('\"'), QStringLiteral("\"\"")) + '\"';
}

void queryToCsv()
{
    QSqlQuery query(conn.mydb);
    query.prepare(" select * from teb1;");
    QFile csvFile ("output.csv");
    if (!csvFile.open(QFile::WriteOnly | QFile::Text)){
        qDebug("failed to open csv file");
        return;
    }
    if (!query.exec()){
        qDebug("failed to run query");
        return;
    }
    QTextStream outStream(&csvFile);
    outStream.setCodec("UTF-8");
    while (query.next()){
        const QSqlRecord record = query.record();
        for (int i=0, recCount = record.count() ; i<recCount ; ++i){
            if (i>0)
                outStream << ','
            outStream << escapedCSV(record.value(i).toString());
        }
        outStream << '\n';
    }
}

sksh

@VRonin
Thank You sir it is work best for me .

Also thanks to other expert for help me.

mrjj

@sksh
super.
Please set as solved.