QTableView is extremely slow (even for only 3000 rows)

I have a table with 3000 rows and 8 columns. I use the QTableView. To insert items I do:

QStandardItem* vSItem = new QStandardItem();
vSItem->setText("Blabla");
mModel->setItem(row, column, vSItem)开发者_如何学运维;

where mModel is QStandardItemModel. Everything is fine if I have not to many rows, but when I am trying to visualize big data (about 3000 rows), then it is extremely slow (20 seconds on Win 7 64-bit (8 core machine with 8 GB of RAM!!!)). Is there anything I can do to improve performance?

Thanks in advance.

Good call on the autoresize on contents for your columns or rows.

I have a function that added a column to the table each time a client connected to my server application. As the number of columns in the table got large, the insertion time seemed to take longer and longer.

I was doing a ui->messageLog->resizeRowsToContents(); each time. I changed this to only auto resize the row that was being added ui->messageLog->resizeRowToContents(0);, and the slowness went away.

Do you have an autoresize on contents for your columns or rows ? It can be a killer in performance sometimes !

Have a look here : QHeaderView::ResizeToContents

Hope it helps !

I found a solution: the problem was that I assigned the model to the tableview already in the constructor. So everytime I inserted the item in the model, tableview was informed and probably updated. Now I assign the model to the tableview only after I filled my model with data. This is not an elegant solution but it works. Is there maybe a way to temporarily disable the model from tableview or something that says to the tableview to not to care about changes in the model?

For this quantity of data, you'd be better with a custom model - then you'd have the control of when you inform the view of updates, for example. The 'standard' items scale to hundreds, and probably thousands, due to modern hardware being fast, but they're explicitly documented as not being intended for datasets of this size.

Also, if all your rows have the same height, setting http://doc.qt.io/qt-5/qtreeview.html#uniformRowHeights-prop to true can boost performance. In my case, a model containing about 50.000 rows was almost unusable with uniformRowHeights set to false (the default). After changing it to true, it worked like a charm.

Watch out for setSectionResizeMode(). This had enormous performance implications for me. It causes row and column size recalculations with every modification (i.e. every setData()/setText() call). This wasn't noticeable until I reached 1000+ rows. Consider using resizeSections() instead which seems to be a one time adjustment.

I am using 80000 rows and had a similar problem adding huge amounts of items to a table.

My solution was to let it allocate the memory in advanced by telling it how many rows it will need.

I was using a Qtableview and model, so:

self.model.setRowCount(80000)

I'm sure you can match this up with your code

try this :

             QSqlDatabase db =QSqlDatabase::addDatabase( "QSQLITE");

      void SELECT_TO_TBLWID(QTableWidget * TBL, QString DbPath,QString SQL)
                  {
                      QSqlDatabase db2 =QSqlDatabase::database();
                      db2.setDatabaseName(DbPath);
                      if( !db2.open() )
                      {
                        qDebug() << db2.lastError();
                        qFatal( "Failed to connect." );
                      }
                        QSqlQuery qry;
                        qry.prepare(SQL);
                        if( !qry.exec() )
                          qDebug() << qry.lastError();
                        else
                        {
                           QSqlRecord rec = qry.record();

                             TBL->setColumnCount(rec.count());
                             int RW=0;
                             for( int r=0; qry.next(); r++ )
                                {RW++;}
                                TBL->setRowCount(RW);
                                for (int pr=RW;qry.previous();pr--){// do nothing}

                         for( int r=0; qry.next(); r++ )
                            {

                              for( int c=0; c<rec.count(); c++ )
                              {
                                  if ( r==0)
                                  {
                                      TBL->setHorizontalHeaderItem(c,new QTableWidgetItem(rec.fieldName(c)));
                                  }

                              TBL->setItem(r, c, new QTableWidgetItem(qry.value(c).toString()));

                              }

                            }
                        }

                        db2.close();
                 }

I had the exact same issue, with even 100 rows the performance was horrible.

Upon inspection this issue is not really related to options set on the table view itself (like resizing and such), but rather because the model informs and updates the view for each insertion (beginInsertRows/endInsertRows).

With that being said you have 2 options for maximum performance:

1. Set the model to the view after you populated with data
2. Set the model anytime, but populate a new list of data and then assign that list to the model

Whichever option you go with, performance is crazy. I went with the second option because I set my model (and proxy model) in the constructor of the widget.

Later on when I want to add data:

// Create a new list of data (temporary)
QList<MyObjects*> NewList;

for (auto it = Result.cbegin(); it != Result.cend(); ++it) 
{
    MyObjects* my = new MyObjects();
    
    // my - set data
    
    NewList.append(my);
}

// Now simply replace current data list
Model->setList(NewList);

This is considering you created your own setList() function inside your custom Model:

void Model::setList(QList<MyObjects*> clist) 
{
    beginResetModel();
    list = clist;
    endResetModel();
}

And voila... you load thousands of records with high performance. Notice beginResetModel() and endResetModel() are the functions that notify the table view.

Enjoy.