qt memory issue QTable widget - qt

Question

I have installed Qt Creator and created a project which will show huge amount of data in a QTableWidget. I have some issue with the memory usage. My project using ~2 GB of RAM when its showing table data. There are nearly 1.4 million rows and each row has 8 columns.
How to solve this issue? Whether the procedure which I used for creating table is wrong?
My code:
main.cpp :
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.cpp :
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
t1 = new QTableWidgetItem();
t2 = new QTableWidgetItem();
t3 = new QTableWidgetItem();
t4 = new QTableWidgetItem();
t5 = new QTableWidgetItem();
t6 = new QTableWidgetItem();
t7 = new QTableWidgetItem();
t8 = new QTableWidgetItem();
qDebug()<<sizeof(t1);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
delete t1;
delete t2;
delete t3;
delete t4;
delete t5;
delete t6;
delete t7;
delete t8;
unsigned int index =0;
ui->tableWidget->setRowCount(1426500);
while (index < 1426500)
{
t1 = new QTableWidgetItem();
t1->setText(QString::number(index));
ui->tableWidget->setItem(index,0,t1);
ui->tableWidget->item(index,0)->setBackgroundColor(QColor(180,150,220));
t2 = new QTableWidgetItem();
t2->setText(QString::number(index));
ui->tableWidget->setItem(index,1,t2);
ui->tableWidget->item(index,1)->setBackgroundColor(QColor(180,150,220));
t3 = new QTableWidgetItem();
t3->setText(QString::number(index));
ui->tableWidget->setItem(index,2,t3);
ui->tableWidget->item(index,2)->setBackgroundColor(QColor(180,150,220));
t4 = new QTableWidgetItem();
t4->setText(QString::number(index));
ui->tableWidget->setItem(index,3,t4);
ui->tableWidget->item(index,3)->setBackgroundColor(QColor(180,150,220));
t5 = new QTableWidgetItem();
t5->setText(QString::number(index));
ui->tableWidget->setItem(index,4,t5);
ui->tableWidget->item(index,4)->setBackgroundColor(QColor(180,150,220));
t6 = new QTableWidgetItem();
t6->setText(QString::number(index));
ui->tableWidget->setItem(index,5,t6);
ui->tableWidget->item(index,5)->setBackgroundColor(QColor(180,150,220));
t7 = new QTableWidgetItem();
t7->setText(QString::number(index));
ui->tableWidget->setItem(index,6,t7);
ui->tableWidget->item(index,6)->setBackgroundColor(QColor(180,150,220));
t8 = new QTableWidgetItem();
t8->setText(QString::number(index));
ui->tableWidget->setItem(index,7,t8);
ui->tableWidget->item(index,7)->setBackgroundColor(QColor(180,150,220));
index++;
}
}
mainwindow.h :
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QTableWidgetItem>
#include <QDebug>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
QTableWidgetItem *t1;
QTableWidgetItem *t2;
QTableWidgetItem *t3;
QTableWidgetItem *t4;
QTableWidgetItem *t5;
QTableWidgetItem *t6;
QTableWidgetItem *t7;
QTableWidgetItem *t8;
private slots:
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
mainwindow.ui :
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>1122</width>
<height>572</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralWidget">
<widget class="QPushButton" name="pushButton">
<property name="geometry">
<rect>
<x>10</x>
<y>0</y>
<width>99</width>
<height>27</height>
</rect>
</property>
<property name="text">
<string>PushButton</string>
</property>
</widget>
<widget class="QTableWidget" name="tableWidget">
<property name="geometry">
<rect>
<x>40</x>
<y>50</y>
<width>1031</width>
<height>441</height>
</rect>
</property>
<property name="columnCount">
<number>8</number>
</property>
<attribute name="horizontalHeaderVisible">
<bool>false</bool>
</attribute>
<column/>
<column/>
<column/>
<column/>
<column/>
<column/>
<column/>
<column/>
</widget>
</widget>
<widget class="QMenuBar" name="menuBar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>1122</width>
<height>25</height>
</rect>
</property>
</widget>
<widget class="QToolBar" name="mainToolBar">
<attribute name="toolBarArea">
<enum>TopToolBarArea</enum>
</attribute>
<attribute name="toolBarBreak">
<bool>false</bool>
</attribute>
</widget>
<widget class="QStatusBar" name="statusBar"/>
</widget>
<layoutdefault spacing="6" margin="11"/>
<resources/>
<connections/>
</ui>
QTableTest.pro :
#-------------------------------------------------
#
# Project created by QtCreator 2017-08-12T12:22:34
#
#-------------------------------------------------
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = QTableTest
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui