Fixes slow update in field calculator

python/core/auto_generated/qgsapplication.sip.in

@@ -824,6 +824,7 @@ Emits the signal to collect all the strings of .qgs to be included in ts file
 .. versionadded:: 3.4
 %End
 
+
 %If (ANDROID)
     //dummy method to workaround sip generation issue
     bool x11EventFilter( XEvent *event );
@@ -852,6 +853,7 @@ In order to register translatable strings, connect to this signal and register t
 .. versionadded:: 3.4
 %End
 
+
 };
 
 

python/core/auto_generated/qgsvectorlayer.sip.in

@@ -2371,6 +2371,13 @@ Is emitted, before changes are committed to the data provider
     void beforeRollBack();
 %Docstring
 Is emitted, before changes are rolled back
+%End
+
+    void afterRollBack();
+%Docstring
+Is emitted, after changes are rolled back
+
+.. versionadded:: 3.4
 %End
 
     void attributeAdded( int idx );

src/app/qgisapp.cpp

@@ -7090,13 +7090,14 @@ void QgisApp::fieldCalculator()
 
 void QgisApp::attributeTable( QgsAttributeTableFilterModel::FilterMode filter )
 {
-  QgsVectorLayer *myLayer = qobject_cast<QgsVectorLayer *>( activeLayer() );
-  if ( !myLayer )
+  QgsVectorLayer *vectorLayer = qobject_cast<QgsVectorLayer *>( activeLayer() );
+  if ( !vectorLayer )
   {
     return;
   }
 
-  QgsAttributeTableDialog *mDialog = new QgsAttributeTableDialog( myLayer, filter );
+  QgsAttributeTableDialog *mDialog = new QgsAttributeTableDialog( vectorLayer, filter );
+
   mDialog->show();
   // the dialog will be deleted by itself on close
 }
@@ -9188,6 +9189,17 @@ bool QgisApp::toggleEditing( QgsMapLayer *layer, bool allowCancel )
   return res;
 }
 
+
+void QgisApp::unblockAttributeTableUpdates( const QgsVectorLayer *layer )
+{
+  emit attributeTableUpdateUnblocked( layer );
+}
+
+void QgisApp::blockAttributeTableUpdates( const QgsVectorLayer *layer )
+{
+  emit attributeTableUpdateBlocked( layer );
+}
+
 void QgisApp::saveActiveLayerEdits()
 {
   saveEdits( activeLayer(), true, true );

src/app/qgisapp.h

@@ -1008,6 +1008,20 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
      */
     void triggerCrashHandler();
 
+    /**
+     * Emits the signal to block updates for attribute tables connected a particular \a layer
+     *
+     * \since QGIS 3.4
+     */
+    void blockAttributeTableUpdates( const QgsVectorLayer *layer );
+
+    /**
+     * Emits the signal to unblock updates for attribute tables connected a particular \a layer
+     *
+     * \since QGIS 3.4
+     */
+    void unblockAttributeTableUpdates( const QgsVectorLayer *layer );
+
   protected:
 
     //! Handle state changes (WindowTitleChange)
@@ -1741,6 +1755,20 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
      */
     void activeLayerChanged( QgsMapLayer *layer );
 
+    /**
+     * Emitted when attribute table updates for a particular \a layer must be blocked
+     *
+     * \since QGIS 3.4
+     */
+    void attributeTableUpdateBlocked( const QgsVectorLayer *layer );
+
+    /**
+     * Emitted when all attribute table updates for a particular \a layer must be unblocked
+     *
+     * \since QGIS 3.4
+     */
+    void attributeTableUpdateUnblocked( const QgsVectorLayer *layer );
+
   private:
     void startProfile( const QString &name );
     void endProfile();

src/app/qgsattributetabledialog.cpp

@@ -111,6 +111,21 @@ QgsAttributeTableDialog::QgsAttributeTableDialog( QgsVectorLayer *layer, QgsAttr
   connect( mActionExpressionSelect, &QAction::triggered, this, &QgsAttributeTableDialog::mActionExpressionSelect_triggered );
   connect( mMainView, &QgsDualView::showContextMenuExternally, this, &QgsAttributeTableDialog::showContextMenu );
 
+  // Block/unblock table updates (feature cache signals)
+  connect( QgisApp::instance(), &QgisApp::attributeTableUpdateBlocked, [ = ]( const QgsVectorLayer * layer )
+  {
+    if ( layer == mLayer )
+      this->blockCacheUpdateSignals( true );
+  } );
+  connect( QgisApp::instance(), &QgisApp::attributeTableUpdateUnblocked, [ = ]( const QgsVectorLayer * layer )
+  {
+    if ( layer == mLayer )
+      this->blockCacheUpdateSignals( false );
+  } );
+  // Massive rollbacks can also freeze the GUI due to the feature cache signals
+  connect( mLayer, &QgsVectorLayer::beforeRollBack, [ = ] { this->blockCacheUpdateSignals( true ); } );
+  connect( mLayer, &QgsVectorLayer::afterRollBack, [ = ] { this->blockCacheUpdateSignals( false ); } );
+
   const QgsFields fields = mLayer->fields();
   for ( const QgsField &field : fields )
   {
@@ -718,7 +733,6 @@ void QgsAttributeTableDialog::mActionOpenFieldCalculator_triggered()
   if ( calc.exec() == QDialog::Accepted )
   {
     int col = masterModel->fieldCol( calc.changedAttributeId() );
-
     if ( col >= 0 )
     {
       masterModel->reload( masterModel->index( 0, col ), masterModel->index( masterModel->rowCount() - 1, col ) );
@@ -1130,6 +1144,15 @@ void QgsAttributeTableDialog::setFilterExpression( const QString &filterString,
   mMainView->setFilterMode( QgsAttributeTableFilterModel::ShowFilteredList );
 }
 
+void QgsAttributeTableDialog::blockCacheUpdateSignals( const bool block )
+{
+  QgsAttributeTableModel *masterModel = mMainView->masterModel();
+
+  if ( ! masterModel )
+    return;
+
+  masterModel->layerCache()->blockSignals( block );
+}
 
 void QgsAttributeTableDialog::deleteFeature( const QgsFeatureId fid )
 {

src/app/qgsattributetabledialog.h

@@ -242,6 +242,7 @@ class APP_EXPORT QgsAttributeTableDialog : public QDialog, private Ui::QgsAttrib
 
     void updateMultiEditButtonState();
     void deleteFeature( QgsFeatureId fid );
+    void blockCacheUpdateSignals( const bool block );
 
     friend class TestQgsAttributeTable;
 };

src/app/qgsfieldcalculator.cpp

@@ -163,8 +163,10 @@ void QgsFieldCalculator::accept()
 {
   builder->saveToRecent( QStringLiteral( "fieldcalc" ) );
 
-  if ( !mVectorLayer )
+  if ( ! mVectorLayer )
+  {
     return;
+  }
 
   // Set up QgsDistanceArea each time we (re-)calculate
   QgsDistanceArea myDa;
@@ -265,6 +267,10 @@ void QgsFieldCalculator::accept()
       return;
     }
 
+    // Begin feature modifications, block updates for attr tables
+    // connected to this layer
+    QgisApp::instance()->blockAttributeTableUpdates( mVectorLayer );
+
     //go through all the features and change the new attribute
     QgsFeature feature;
     bool calculationSuccess = true;
@@ -315,6 +321,8 @@ void QgsFieldCalculator::accept()
       rownum++;
     }
 
+    QgisApp::instance()->unblockAttributeTableUpdates( mVectorLayer );
+
     QApplication::restoreOverrideCursor();
 
     if ( !calculationSuccess )
@@ -323,7 +331,6 @@ void QgsFieldCalculator::accept()
       mVectorLayer->destroyEditCommand();
       return;
     }
-
     mVectorLayer->endEditCommand();
   }
   QDialog::accept();

src/core/qgsapplication.cpp

@@ -1535,6 +1535,7 @@ void QgsApplication::collectTranslatableObjects( QgsTranslationContext *translat
   emit requestForTranslatableObjects( translationContext );
 }
 
+
 QString QgsApplication::nullRepresentation()
 {
   ApplicationMembers *appMembers = members();

src/core/qgsapplication.h

@@ -757,6 +757,7 @@ class CORE_EXPORT QgsApplication : public QApplication
      */
     void collectTranslatableObjects( QgsTranslationContext *translationContext );
 
+
 #ifdef SIP_RUN
     SIP_IF_FEATURE( ANDROID )
     //dummy method to workaround sip generation issue
@@ -788,6 +789,7 @@ class CORE_EXPORT QgsApplication : public QApplication
      */
     void requestForTranslatableObjects( QgsTranslationContext *translationContext );
 
+
   private:
 
     static void copyPath( const QString &src, const QString &dst );

src/core/qgsvectorlayer.cpp

@@ -2973,6 +2973,8 @@ bool QgsVectorLayer::rollBack( bool deleteBuffer )
 
   mEditBuffer->rollBack();
 
+  emit afterRollBack();
+
   if ( isModified() )
   {
     // new undo stack roll back method

src/core/qgsvectorlayer.h

@@ -2167,6 +2167,12 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
     //! Is emitted, before changes are rolled back
     void beforeRollBack();
 
+    /**
+     * Is emitted, after changes are rolled back
+     * \since QGIS 3.4
+     */
+    void afterRollBack();
+
     /**
      * Will be emitted, when a new attribute has been added to this vector layer.
      * Applies only to types QgsFields::OriginEdit, QgsFields::OriginProvider and QgsFields::OriginExpression