Move fetching data for data browsing to a separate thread

This moves the data fetching code into a separate thread for
asynchronous execution. The Browse Data and the Execute SQL tabs are
affected by this.

Note that this is a somewhat naive implementation that is meant for some
first testing.

CMakeLists.txt

@@ -117,6 +117,7 @@ set(SQLB_MOC_HDR
 	src/PlotDock.h
 	src/RemoteDock.h
 	src/RemoteModel.h
+	src/SqlThread.h
 )
 
 set(SQLB_SRC
@@ -154,6 +155,7 @@ set(SQLB_SRC
 	src/PlotDock.cpp
 	src/RemoteDock.cpp
 	src/RemoteModel.cpp
+	src/SqlThread.cpp
 )
 
 set(SQLB_FORMS

src/SqlThread.cpp

@@ -0,0 +1,49 @@
+#include "SqlThread.h"
+#include "sqlitedb.h"
+#include "sqlite.h"
+
+SqlThread::SqlThread(DBBrowserDB& db, const QString& query, int column_count, QList<QByteArrayList>& result)
+    : m_db(db),
+      m_query(query),
+      m_columnCount(column_count),
+      m_result(result)
+{
+}
+
+void SqlThread::run()
+{
+    // Prepare statement
+    QByteArray utf8Query = m_query.toUtf8();
+    sqlite3_stmt *stmt;
+    if(sqlite3_prepare_v2(m_db._db, utf8Query, utf8Query.size(), &stmt, NULL) == SQLITE_OK)
+    {
+        // Fetch rows
+        while(sqlite3_step(stmt) == SQLITE_ROW)
+        {
+            // Fetch columns
+            QByteArrayList rowdata;
+            for(int i=0;i<m_columnCount;++i)
+            {
+                // Null?
+                if(sqlite3_column_type(stmt, i) == SQLITE_NULL)
+                {
+                    rowdata.append(QByteArray());
+                } else {
+                    // Some data or empty string?
+                    int bytes = sqlite3_column_bytes(stmt, i);
+                    if(bytes)
+                        rowdata.append(QByteArray(static_cast<const char*>(sqlite3_column_blob(stmt, i)), bytes));
+                    else
+                        rowdata.append(QByteArray(""));
+                }
+            }
+
+            // Save row
+            m_result.push_back(rowdata);
+        }
+    }
+
+    // Clean up
+    sqlite3_finalize(stmt);
+    emit done();
+}

src/SqlThread.h

@@ -0,0 +1,27 @@
+#ifndef SQLTHREAD_H
+#define SQLTHREAD_H
+
+#include <QThread>
+
+class DBBrowserDB;
+
+class SqlThread : public QThread
+{
+    Q_OBJECT
+
+public:
+    SqlThread(DBBrowserDB& db, const QString& query, int column_count, QList<QByteArrayList>& result);
+
+    void run();
+
+signals:
+    void done();
+
+private:
+    DBBrowserDB& m_db;
+    QString m_query;
+    int m_columnCount;
+    QList<QByteArrayList>& m_result;
+};
+
+#endif

src/sqlitetablemodel.cpp

@@ -2,6 +2,7 @@
 #include "sqlitedb.h"
 #include "sqlite.h"
 #include "Settings.h"
+#include "SqlThread.h"
 
 #include <QDebug>
 #include <QMessageBox>
@@ -494,39 +495,19 @@ void SqliteTableModel::fetchData(unsigned int from, unsigned to)
             sLimitQuery = queryTemp + QString(" LIMIT %1, %2;").arg(from).arg(to-from);
     }
     m_db.logSQL(sLimitQuery, kLogMsg_App);
-    QByteArray utf8Query = sLimitQuery.toUtf8();
-    sqlite3_stmt *stmt;
-    int status = sqlite3_prepare_v2(m_db._db, utf8Query, utf8Query.size(), &stmt, NULL);
 
-    if(SQLITE_OK == status)
-    {
-        while(sqlite3_step(stmt) == SQLITE_ROW)
+    // Fetch data in separate thread
+    SqlThread* thread = new SqlThread(m_db, sLimitQuery, m_headers.size(), m_data);
+    connect(thread, &SqlThread::done, [this, currentsize]() {
+        // Check if there was any new data
+        if(m_data.size() > currentsize)
         {
-            QByteArrayList rowdata;
-            for (int i = 0; i < m_headers.size(); ++i)
-            {
-                if(sqlite3_column_type(stmt, i) == SQLITE_NULL)
-                {
-                    rowdata.append(QByteArray());
-                } else {
-                    int bytes = sqlite3_column_bytes(stmt, i);
-                    if(bytes)
-                        rowdata.append(QByteArray(static_cast<const char*>(sqlite3_column_blob(stmt, i)), bytes));
-                    else
-                        rowdata.append(QByteArray(""));
-                }
-            }
-            m_data.push_back(rowdata);
+            beginInsertRows(QModelIndex(), currentsize, m_data.size()-1);
+            endInsertRows();
         }
-    }
-    sqlite3_finalize(stmt);
-
-    // Check if there was any new data
-    if(m_data.size() > currentsize)
-    {
-        beginInsertRows(QModelIndex(), currentsize, m_data.size()-1);
-        endInsertRows();
-    }
+    });
+    connect(thread, &SqlThread::finished, thread, &QObject::deleteLater);
+    thread->start();
 }
 
 void SqliteTableModel::buildQuery()

src/src.pro

@@ -56,7 +56,8 @@ HEADERS += \
     ForeignKeyEditorDelegate.h \
     PlotDock.h \
     RemoteDock.h \
-    RemoteModel.h
+    RemoteModel.h \
+    SqlThread.h
 
 SOURCES += \
     sqlitedb.cpp \
@@ -91,7 +92,8 @@ SOURCES += \
     ForeignKeyEditorDelegate.cpp \
     PlotDock.cpp \
     RemoteDock.cpp \
-    RemoteModel.cpp
+    RemoteModel.cpp \
+    SqlThread.cpp
 
 RESOURCES += icons/icons.qrc \
              translations/flags/flags.qrc \