Fix remaining issue with optimised SELECT statements

This fixes a remaining issue which was introduced in the series of
commits made for improving the performance of running SELECT statements
in the Execute SQL tab. The problem here was that rerunning a query did
not show any results in the view.

See issue #2165.

src/RowLoader.cpp

@@ -233,11 +233,11 @@ void RowLoader::process (Task & t)
         const bool first_chunk = !cache_data.initialised();
         if(first_chunk)
         {
-            size_t num_columns = static_cast<size_t>(sqlite3_column_count(stmt));
-            for(size_t i=0;i<num_columns;++i)
+            int num_columns = sqlite3_column_count(stmt);
+            for(int i=0;i<num_columns;++i)
             {
-                headers.push_back(sqlite3_column_name(stmt, static_cast<int>(i)));
-                data_types.push_back(sqlite3_column_type(stmt, static_cast<int>(i)));
+                headers.push_back(sqlite3_column_name(stmt, i));
+                data_types.push_back(sqlite3_column_type(stmt, i));
             }
         }
 
@@ -271,8 +271,6 @@ void RowLoader::process (Task & t)
         // If there is no need to query the row count this means the number of rows we just got is the total row count.
         if(first_chunk)
         {
-            cache_data.setInitialised();
-
             if(row == t.row_end)
                 triggerRowCountDetermination(t.token);
             else

src/sqlitetablemodel.cpp

@@ -67,17 +67,19 @@ void SqliteTableModel::handleFinishedFetch (int life_id, unsigned int fetched_ro
 
     Q_ASSERT(fetched_row_end >= fetched_row_begin);
 
-    // Tell the query object about the column names. We also use this property to determine if the number of columns changed for some
-    // reason and if so, we tell the view to update the table layout.
-    if(m_query.columnNames().size() != m_headers.size())
+    // Tell the query object about the column names
+    m_query.setColumNames(m_headers);
+
+    // If the cache has been uninitialised so far we set it to initialised now and
+    // tell the view to update the table layout.
+    if(!m_cache.initialised())
     {
+        m_cache.setInitialised();
         emit layoutChanged();
         emit columnsChanged();
     }
-    m_query.setColumNames(m_headers);
 
     auto old_row_count = m_currentRowCount;
-
     auto new_row_count = std::max(old_row_count, fetched_row_begin);
     new_row_count = std::max(new_row_count, fetched_row_end);
     Q_ASSERT(new_row_count >= old_row_count);