Added all files

main.cpp

@@ -0,0 +1,15 @@
+#include "mainwindow.h"
+#include <QApplication>
+
+
+int main(int argc, char *argv[])
+{
+    QApplication a(argc, argv);
+
+    MainWindow w;
+//    w.show();
+
+    w.startRace();
+
+    return a.exec();
+}

mainwindow.cpp

@@ -0,0 +1,168 @@
+#include "mainwindow.h"
+#include "ui_mainwindow.h"
+#include "sleeperthread.h"
+
+#include <QDateTime>
+#include <QDebug>
+#include <QSqlError>
+#include <QSqlQuery>
+#include <QSqlRecord>
+#include <QThread>
+
+#include <QtConcurrentRun>
+#include <QFuture>
+
+const QString tableName = QString ("test_table");
+const QString createTableText = QString("CREATE TABLE IF NOT EXISTS test_table "
+                                        "( id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL UNIQUE, "
+                                        "test_string CHAR( 255 ) )");
+const QString connectionName = QString("main_connection");
+
+const QString insertStartInfo = QString("INSERT INTO %1 (test_string) VALUES ('START: %2')")
+        .arg(tableName)
+        .arg(QDateTime::currentDateTime().toString());
+
+const QString selectQuery = QString("SELECT * from %1").arg(tableName);
+
+MainWindow::MainWindow(QWidget *parent) :
+    QMainWindow(parent),
+    ui(new Ui::MainWindow)
+{
+    ui->setupUi(this);
+    if (!prepareAndOpenDb()) {
+        qDebug() << "Error while opening DB";
+    }
+}
+
+bool MainWindow::prepareAndOpenDb()
+{
+    QStringList driverList( QSqlDatabase::drivers() );
+
+    if (!driverList.contains(QString("QSQLITE"), Qt::CaseInsensitive)) {
+        qDebug() << "No SQLITE support";
+        return false;
+    } else {
+        qDebug() << "SQLITE support is present";
+    }
+
+    mWorkDb = QSqlDatabase::addDatabase("QSQLITE", connectionName);
+    mWorkDb.setHostName("localhost");
+    mWorkDb.setDatabaseName("sqlitetest");
+
+    if (!mWorkDb.open()) {
+        qDebug() << "DB was not opened!";
+        return false;
+    }
+
+//    QString journalMode("OFF"); // default: "DELETE", "WAL"
+//    if (setDbJournalMode(mWorkDb, journalMode) )
+//    {
+//        qDebug() << "Sucessfuly switched to" << journalMode;
+//    }
+
+    QStringList tables = mWorkDb.tables(QSql::Tables);
+
+    if ( !tables.contains("test_table") ) {
+        QSqlQuery createTableQuery(mWorkDb);
+        if ( !createTableQuery.exec(createTableText) ) {
+            qDebug() << "Can't create table" << tableName << "in" << mWorkDb.databaseName()
+                     << ":" << createTableQuery.lastError().text();
+            return false;
+        }
+    } else {
+        qDebug() << mWorkDb.databaseName() << "already has table" << tableName;
+    }
+    QSqlQuery q(insertStartInfo, mWorkDb);
+    return true;
+}
+
+bool MainWindow::setDbJournalMode(QSqlDatabase &db, const QString &mode)
+{
+    QSqlQuery q(db);
+    q.prepare( QString("PRAGMA journal_mode = %1").arg(mode) );
+    return q.exec();
+}
+
+void MainWindow::readFromDb()
+{
+    const int threadId = QThread::currentThreadId();
+    qDebug() << "READER:" << threadId;
+
+    // wait for transaction in writer begins
+    while (transInProcess==false)
+    {
+        qDebug() << "  # Reader is waiting";
+        SleeperThread::msSleep(7);
+    }
+    qDebug() << "# reader got transInProcess==true";
+    QString connectionName = QString ("Reader_%1").arg(threadId);
+
+    QSqlDatabase readDb = QSqlDatabase::cloneDatabase(mWorkDb, connectionName);
+
+    if (!readDb.open()) {
+        qDebug() << "DB was not opened to read!";
+        return;
+    }
+
+    QSqlQuery q(selectQuery, readDb);
+    q.exec();
+    outpuQuery(q);
+}
+
+void MainWindow::writeToDb()
+{
+    const int threadId = QThread::currentThreadId();
+    qDebug() << "WRITER:" << threadId;
+
+    QString connectionName = QString ("Writer_%1").arg(threadId);
+    QSqlDatabase writeDb = QSqlDatabase::cloneDatabase(mWorkDb, connectionName);
+
+    if (!writeDb.open()) {
+        qDebug() << "DB was not opened to write!";
+        return;
+    }
+
+    const QString insertWriterInfo = QString("INSERT INTO %1 (test_string) VALUES ('WRITER at %2, %3')")
+            .arg(tableName)
+            .arg(QString::number(threadId))
+            .arg(QDateTime::currentDateTime().toString());
+
+    // insert some pause just to feel waiting process in Reader
+    SleeperThread::msSleep(21);
+    writeDb.transaction();
+    transInProcess = true;
+    SleeperThread::msSleep(21);
+    QSqlQuery q(insertWriterInfo, writeDb);
+    writeDb.commit();
+    transInProcess = false;
+}
+
+void MainWindow::startRace()
+{
+    transInProcess = false;
+    QtConcurrent::run(this, &MainWindow::readFromDb);
+    QtConcurrent::run(this, &MainWindow::writeToDb);
+
+    // probably all queries will be applied
+    SleeperThread::msSleep(600);
+    qDebug() << "Summary:";
+    QSqlQuery q(selectQuery, mWorkDb);
+    q.exec();
+    outpuQuery(q);
+}
+
+
+MainWindow::~MainWindow()
+{
+    delete ui;
+}
+
+
+void MainWindow::outpuQuery(QSqlQuery &query)
+{
+    if (query.isActive()) {
+        while (query.next()) {
+            qDebug("%4i: %s", query.value(0).toInt(), qPrintable(query.value(1).toString())); // << query.value(0).toInt() << ":" << query.value(1).toString();
+        }
+    }
+}

mainwindow.h

@@ -0,0 +1,33 @@
+#ifndef MAINWINDOW_H
+#define MAINWINDOW_H
+
+#include <QMainWindow>
+#include <QSqlDatabase>
+
+class QSqlQuery;
+
+namespace Ui {
+class MainWindow;
+}
+
+class MainWindow : public QMainWindow
+{
+    Q_OBJECT
+    QSqlDatabase mWorkDb;
+public:
+    explicit MainWindow(QWidget *parent = 0);
+    ~MainWindow();
+
+    bool prepareAndOpenDb();
+    bool setDbJournalMode(QSqlDatabase& db,  const QString& mode);
+    void readFromDb();
+    void writeToDb();
+    void startRace();
+    void outpuQuery(QSqlQuery& query);
+    volatile bool transInProcess;
+
+private:
+    Ui::MainWindow *ui;
+};
+
+#endif // MAINWINDOW_H

mainwindow.ui

@@ -0,0 +1,24 @@
+<ui version="4.0">
+ <class>MainWindow</class>
+ <widget class="QMainWindow" name="MainWindow" >
+  <property name="geometry" >
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>400</width>
+    <height>300</height>
+   </rect>
+  </property>
+  <property name="windowTitle" >
+   <string>MainWindow</string>
+  </property>
+  <widget class="QMenuBar" name="menuBar" />
+  <widget class="QToolBar" name="mainToolBar" />
+  <widget class="QWidget" name="centralWidget" />
+  <widget class="QStatusBar" name="statusBar" />
+ </widget>
+ <layoutDefault spacing="6" margin="11" />
+ <pixmapfunction></pixmapfunction>
+ <resources/>
+ <connections/>
+</ui>

sleeperthread.h

@@ -0,0 +1,23 @@
+#ifndef SLEEPERTHREAD_H
+#define SLEEPERTHREAD_H
+
+#include <QThread>
+
+class SleeperThread : public QThread
+{
+    Q_OBJECT
+public:
+    static void msSleep(uint ms) {
+        if ( !ms ) { return; }
+
+        SleeperThread sleeper(ms);
+        sleeper.run();
+    }
+    explicit SleeperThread(uint ms) : m_sleepTime(ms) {}
+    virtual void run() { msleep( m_sleepTime );}
+    void setSleepTime(uint ms) { m_sleepTime = ms ;}
+    uint sleepTime() const { return m_sleepTime; }
+private:
+    uint m_sleepTime;
+};
+#endif // SLEEPERTHREAD_H

sqlite_test.pro

@@ -0,0 +1,21 @@
+#-------------------------------------------------
+#
+# Project created by QtCreator 2013-07-10T21:33:13
+#
+#-------------------------------------------------
+
+QT       += core gui sql
+
+greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
+
+TARGET = sqlite_test
+TEMPLATE = app
+
+
+SOURCES += main.cpp\
+        mainwindow.cpp
+
+HEADERS  += mainwindow.h \
+    sleeperthread.h
+
+FORMS    += mainwindow.ui