QTableView is extremely slow (even for only 3000 r

问题:

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);

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.

回答1:

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.

回答2:

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?

回答3:

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.

回答4:

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 !

回答5:

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.

回答6:

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();
                 }

回答7:

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

回答8:

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.