Avoid unnecessary reloads layer for attribute table

On behalf of Faunalia, sponsored by ENEL

Author: nyalldawson

python/gui/attributetable/qgsdualview.sip

@@ -32,16 +32,8 @@ class QgsDualView : QStackedWidget
     explicit QgsDualView( QWidget* parent /TransferThis/ = 0 );
     virtual ~QgsDualView();
 
-    /**
-     * Has to be called to initialize the dual view.
-     *
-     * @param layer      The layer which should be used to fetch features
-     * @param mapCanvas  The mapCanvas (used for the FilterMode
-     *                   {@link QgsAttributeTableFilterModel::ShowVisible}
-     * @param request    Use a modified request to limit the shown features
-     * @param context    The context in which this view is shown
-     */
-    void init( QgsVectorLayer* layer, QgsMapCanvas* mapCanvas, const QgsFeatureRequest& request = QgsFeatureRequest(), const QgsAttributeEditorContext& context = QgsAttributeEditorContext() );
+    void init( QgsVectorLayer* layer, QgsMapCanvas* mapCanvas, const QgsFeatureRequest& request = QgsFeatureRequest(), const QgsAttributeEditorContext& context = QgsAttributeEditorContext(),
+               bool loadFeatures = true );
 
     /**
      * Change the current view mode.

src/app/qgsattributetabledialog.cpp

@@ -157,7 +157,7 @@ QgsAttributeTableDialog::QgsAttributeTableDialog( QgsVectorLayer *layer, QWidget
     r.setFlags( QgsFeatureRequest::NoGeometry );
 
   // Initialize dual view
-  mMainView->init( mLayer, QgisApp::instance()->mapCanvas(), r, mEditorContext );
+  mMainView->init( mLayer, QgisApp::instance()->mapCanvas(), r, mEditorContext, false );
 
   QgsAttributeTableConfig config = mLayer->attributeTableConfig();
   mMainView->setAttributeTableConfig( config );

src/gui/attributetable/qgsdualview.cpp

@@ -68,7 +68,7 @@ QgsDualView::QgsDualView( QWidget *parent )
   connect( mFeatureList, &QgsFeatureListView::displayExpressionChanged, this, &QgsDualView::previewExpressionChanged );
 }
 
-void QgsDualView::init( QgsVectorLayer *layer, QgsMapCanvas *mapCanvas, const QgsFeatureRequest &request, const QgsAttributeEditorContext &context )
+void QgsDualView::init( QgsVectorLayer *layer, QgsMapCanvas *mapCanvas, const QgsFeatureRequest &request, const QgsAttributeEditorContext &context, bool loadFeatures )
 {
   mMapCanvas = mapCanvas;
 
@@ -85,7 +85,7 @@ void QgsDualView::init( QgsVectorLayer *layer, QgsMapCanvas *mapCanvas, const Qg
   connect( mTableView, &QgsAttributeTableView::columnResized, this, &QgsDualView::tableColumnResized );
 
   initLayerCache( !( request.flags() & QgsFeatureRequest::NoGeometry ) || !request.filterRect().isNull() );
-  initModels( mapCanvas, request );
+  initModels( mapCanvas, request, loadFeatures );
 
   mConditionalFormatWidget->setLayer( mLayer );
 
@@ -194,9 +194,6 @@ QgsDualView::ViewMode QgsDualView::view() const
 
 void QgsDualView::setFilterMode( QgsAttributeTableFilterModel::FilterMode filterMode )
 {
-  if ( mFilterModel->filterMode() == filterMode )
-    return;
-
   // cleanup any existing connections
   switch ( mFilterModel->filterMode() )
   {
@@ -217,17 +214,23 @@ void QgsDualView::setFilterMode( QgsAttributeTableFilterModel::FilterMode filter
   QgsFeatureRequest r = mMasterModel->request();
   bool needsGeometry = filterMode == QgsAttributeTableFilterModel::ShowVisible;
 
+  bool requiresTableReload = ( r.filterType() != QgsFeatureRequest::FilterNone || !r.filterRect().isNull() ) // previous request was subset
+                             || ( needsGeometry && r.flags() & QgsFeatureRequest::NoGeometry ) // no geometry for last request
+                             || ( mMasterModel->rowCount() == 0 ); // no features
+
   if ( !needsGeometry )
     r.setFlags( r.flags() | QgsFeatureRequest::NoGeometry );
   else
     r.setFlags( r.flags() & ~( QgsFeatureRequest::NoGeometry ) );
+  r.setFilterFids( QgsFeatureIds() );
+  r.setFilterRect( QgsRectangle() );
+  r.disableFilter();
 
+  // setup new connections and filter request parameters
   switch ( filterMode )
   {
     case QgsAttributeTableFilterModel::ShowVisible:
       connect( mMapCanvas, &QgsMapCanvas::extentsChanged, this, &QgsDualView::extentChanged );
-      r.setFilterFids( QgsFeatureIds() );
-      r.disableFilter();
       if ( mMapCanvas )
       {
         QgsRectangle rect = mMapCanvas->mapSettings().mapToLayerCoordinates( mLayer, mMapCanvas->extent() );
@@ -238,23 +241,23 @@ void QgsDualView::setFilterMode( QgsAttributeTableFilterModel::FilterMode filter
     case QgsAttributeTableFilterModel::ShowAll:
     case QgsAttributeTableFilterModel::ShowEdited:
     case QgsAttributeTableFilterModel::ShowFilteredList:
-      r.setFilterFids( QgsFeatureIds() );
-      r.disableFilter();
       break;
 
     case QgsAttributeTableFilterModel::ShowSelected:
       connect( masterModel()->layer(), &QgsVectorLayer::selectionChanged, this, &QgsDualView::updateSelectedFeatures );
       if ( masterModel()->layer()->selectedFeatureCount() > 0 )
         r.setFilterFids( masterModel()->layer()->selectedFeatureIds() );
-      else
-        r.disableFilter();
       break;
   }
 
-  mMasterModel->setRequest( r );
-  whileBlocking( mLayerCache )->setCacheGeometry( needsGeometry );
-  mMasterModel->loadLayer();
+  if ( requiresTableReload )
+  {
+    mMasterModel->setRequest( r );
+    whileBlocking( mLayerCache )->setCacheGeometry( needsGeometry );
+    mMasterModel->loadLayer();
+  }
 
+  //update filter model
   mFilterModel->setFilterMode( filterMode );
   emit filterChanged();
 }
@@ -278,7 +281,7 @@ void QgsDualView::initLayerCache( bool cacheGeometry )
   }
 }
 
-void QgsDualView::initModels( QgsMapCanvas *mapCanvas, const QgsFeatureRequest &request )
+void QgsDualView::initModels( QgsMapCanvas *mapCanvas, const QgsFeatureRequest &request, bool loadFeatures )
 {
   delete mFeatureListModel;
   delete mFilterModel;
@@ -294,7 +297,8 @@ void QgsDualView::initModels( QgsMapCanvas *mapCanvas, const QgsFeatureRequest &
 
   connect( mConditionalFormatWidget, &QgsFieldConditionalFormatWidget::rulesUpdated, mMasterModel, &QgsAttributeTableModel::fieldConditionalStyleChanged );
 
-  mMasterModel->loadLayer();
+  if ( loadFeatures )
+    mMasterModel->loadLayer();
 
   mFilterModel = new QgsAttributeTableFilterModel( mapCanvas, mMasterModel, mMasterModel );
 
@@ -711,6 +715,9 @@ void QgsDualView::sortByPreviewExpression()
 void QgsDualView::updateSelectedFeatures()
 {
   QgsFeatureRequest r = mMasterModel->request();
+  if ( r.filterType() == QgsFeatureRequest::FilterNone && r.filterRect().isNull() )
+    return; // already requested all features
+
   if ( masterModel()->layer()->selectedFeatureCount() > 0 )
     r.setFilterFids( masterModel()->layer()->selectedFeatureIds() );
   else
@@ -722,13 +729,13 @@ void QgsDualView::updateSelectedFeatures()
 void QgsDualView::extentChanged()
 {
   QgsFeatureRequest r = mMasterModel->request();
-  if ( mMapCanvas )
+  if ( mMapCanvas && ( r.filterType() != QgsFeatureRequest::FilterNone || !r.filterRect().isNull() ) )
   {
     QgsRectangle rect = mMapCanvas->mapSettings().mapToLayerCoordinates( mLayer, mMapCanvas->extent() );
     r.setFilterRect( rect );
+    mMasterModel->setRequest( r );
+    mMasterModel->loadLayer();
   }
-  mMasterModel->setRequest( r );
-  mMasterModel->loadLayer();
 }
 
 void QgsDualView::featureFormAttributeChanged()

src/gui/attributetable/qgsdualview.h

@@ -80,8 +80,11 @@ class GUI_EXPORT QgsDualView : public QStackedWidget, private Ui::QgsDualViewBas
      *                   {@link QgsAttributeTableFilterModel::ShowVisible}
      * @param request    Use a modified request to limit the shown features
      * @param context    The context in which this view is shown
+     * @param loadFeatures whether to initially load all features into the view. If set to
+     * false, limited features can later be loaded using setFilterMode()
      */
-    void init( QgsVectorLayer *layer, QgsMapCanvas *mapCanvas, const QgsFeatureRequest &request = QgsFeatureRequest(), const QgsAttributeEditorContext &context = QgsAttributeEditorContext() );
+    void init( QgsVectorLayer *layer, QgsMapCanvas *mapCanvas, const QgsFeatureRequest &request = QgsFeatureRequest(), const QgsAttributeEditorContext &context = QgsAttributeEditorContext(),
+               bool loadFeatures = true );
 
     /**
      * Change the current view mode.