diff --git a/python/core/qgsvectorlayerjoinbuffer.sip b/python/core/qgsvectorlayerjoinbuffer.sip
index bdc45784c346..0484c3eab3ed 100644
--- a/python/core/qgsvectorlayerjoinbuffer.sip
+++ b/python/core/qgsvectorlayerjoinbuffer.sip
@@ -132,6 +132,82 @@ Quick way to test if there is any join at all
  :rtype: QgsVectorLayerJoinBuffer
 %End
 
+    bool addFeature( const QgsFeature &feature ) const;
+%Docstring
+ Adds a feature in joined layers. The feature given in parameter is the
+ one added in target layer. If a corresponding joined feature yet exists
+ in a joined layer, then this feature is just updated. Note that if a
+ corresponding joined feature has only empty fields, then it's not
+ created nor added.
+
+ \param feature The feature added in the target layer.
+
+ :return: false if an error happened, true otherwise
+
+.. versionadded:: 3.0
+ :rtype: bool
+%End
+
+    bool addFeatures( const QgsFeatureList &features ) const;
+%Docstring
+ Adds a list of features in joined layers. Features given in parameter
+ are those added in target layer. If a corresponding joined feature yet
+ exists in a joined layer, then this feature is just updated. Note that
+ if a corresponding joined feature has only empty fields, then it's not
+ created nor added.
+
+ \param features The list of features added in the target layer
+
+ :return: false if an error happened, true otherwise
+
+.. versionadded:: 3.0
+ :rtype: bool
+%End
+
+    bool changeAttributeValue( QgsFeatureId fid, int field, const QVariant &newValue, const QVariant &oldValue = QVariant() ) const;
+%Docstring
+ Changes attribute value in joined layers. The feature id given in
+ parameter is the one added in target layer. If the corresponding joined
+ feature does not exist in a joined layer, then it's automatically
+ created if its fields are not empty.
+
+ \param fid The feature id
+ \param field The field to update
+ \param newValue The new value of the attribute
+ \param oldValue The old value of the attribute
+
+ :return: false if an error happened, true otherwise
+
+.. versionadded:: 3.0
+ :rtype: bool
+%End
+
+    bool deleteFeature( QgsFeatureId fid ) const;
+%Docstring
+ Deletes a feature from joined layers. The feature id given in
+ parameter is the one coming from the target layer.
+
+ \param fid The feature id from the target layer to delete
+
+ :return: false if an error happened, true otherwise
+
+.. versionadded:: 3.0
+ :rtype: bool
+%End
+
+    bool deleteFeatures( const QgsFeatureIds &fids ) const;
+%Docstring
+ Deletes a list of features from joined layers. Feature ids given
+ in aprameter are those coming from the target layer.
+
+ \param fids Feature ids from the target layer to delete
+
+ :return: false if an error happened, true otherwise
+
+.. versionadded:: 3.0
+ :rtype: bool
+%End
+
   signals:
     void joinedFieldsChanged();
 %Docstring
diff --git a/src/core/qgsvectorlayer.cpp b/src/core/qgsvectorlayer.cpp
index e8f1002455dc..b105ae6bba3f 100644
--- a/src/core/qgsvectorlayer.cpp
+++ b/src/core/qgsvectorlayer.cpp
@@ -951,7 +951,7 @@ bool QgsVectorLayer::addFeature( QgsFeature &feature, Flags )
     updateExtents();
 
     if ( mJoinBuffer->containsJoins() )
-      success = addFeaturesToJoinedLayers( QgsFeatureList() << feature );
+      success = mJoinBuffer->addFeature( feature );
   }
 
   return success;
@@ -2265,27 +2265,7 @@ bool QgsVectorLayer::changeAttributeValue( QgsFeatureId fid, int field, const QV
 {
   if ( fields().fieldOrigin( field ) == QgsFields::OriginJoin )
   {
-    int srcFieldIndex;
-    const QgsVectorLayerJoinInfo *info = mJoinBuffer->joinForFieldIndex( field, fields(), srcFieldIndex );
-    if ( info && info->joinLayer() && info->isEditable() )
-    {
-      QgsFeature feature = getFeature( fid );
-
-      if ( !feature.isValid() )
-        return false;
-
-      const QgsFeature joinFeature = mJoinBuffer->joinedFeatureOf( info, feature );
-
-      if ( joinFeature.isValid() )
-        return info->joinLayer()->changeAttributeValue( joinFeature.id(), srcFieldIndex, newValue, oldValue );
-      else
-      {
-        feature.setAttribute( field, newValue );
-        return addFeaturesToJoinedLayers( QgsFeatureList() << feature );
-      }
-    }
-    else
-      return false;
+    return mJoinBuffer->changeAttributeValue( fid, field, newValue, oldValue );
   }
   else
   {
@@ -2442,7 +2422,7 @@ bool QgsVectorLayer::deleteFeature( QgsFeatureId fid )
     return false;
 
   if ( mJoinBuffer->containsJoins() )
-    deleteFeaturesFromJoinedLayers( QgsFeatureIds() << fid );
+    mJoinBuffer->deleteFeature( fid );
 
   bool res = mEditBuffer->deleteFeature( fid );
   if ( res )
@@ -2463,7 +2443,7 @@ bool QgsVectorLayer::deleteFeatures( const QgsFeatureIds &fids )
   }
 
   if ( mJoinBuffer->containsJoins() )
-    deleteFeaturesFromJoinedLayers( fids );
+    mJoinBuffer->deleteFeatures( fids );
 
   bool res = mEditBuffer->deleteFeatures( fids );
 
@@ -2476,26 +2456,6 @@ bool QgsVectorLayer::deleteFeatures( const QgsFeatureIds &fids )
   return res;
 }
 
-bool QgsVectorLayer::deleteFeaturesFromJoinedLayers( QgsFeatureIds fids )
-{
-  bool rc = false;
-
-  Q_FOREACH ( const QgsFeatureId &fid, fids )
-  {
-    Q_FOREACH ( const QgsVectorLayerJoinInfo &info, vectorJoins() )
-    {
-      if ( info.isEditable() && info.hasCascadedDelete() )
-      {
-        const QgsFeature joinFeature = mJoinBuffer->joinedFeatureOf( &info, getFeature( fid ) );
-        if ( joinFeature.isValid() )
-          info.joinLayer()->deleteFeature( joinFeature.id() );
-      }
-    }
-  }
-
-  return rc;
-}
-
 QgsAttributeList QgsVectorLayer::pkAttributeList() const
 {
   QgsAttributeList pkAttributesList;
@@ -2668,83 +2628,11 @@ bool QgsVectorLayer::addFeatures( QgsFeatureList &features, Flags )
   updateExtents();
 
   if ( res && mJoinBuffer->containsJoins() )
-    res = addFeaturesToJoinedLayers( features );
+    res = mJoinBuffer->addFeatures( features );
 
   return res;
 }
 
-bool QgsVectorLayer::addFeaturesToJoinedLayers( QgsFeatureList &features, Flags )
-{
-  // try to add/update a feature in each joined layer
-  Q_FOREACH ( const QgsVectorLayerJoinInfo &info, vectorJoins() )
-  {
-    QgsVectorLayer *joinLayer = info.joinLayer();
-
-    if ( joinLayer && joinLayer->isEditable() && info.isEditable() && info.hasUpsertOnEdit() )
-    {
-      QgsFeatureList joinFeatures;
-
-      Q_FOREACH ( const QgsFeature &feature, features )
-      {
-        const QgsFeature joinFeature = info.extractJoinedFeature( feature );
-
-        // we don't want to add a new feature in joined layer when the id
-        // column value yet exist, we just want to update the existing one
-        const QVariant idFieldValue = feature.attribute( info.targetFieldName() );
-        const QString filter = QgsExpression::createFieldEqualityExpression( info.joinFieldName(), idFieldValue.toString() );
-
-        QgsFeatureRequest request;
-        request.setFilterExpression( filter );
-        request.setLimit( 1 );
-
-        QgsFeatureIterator it = info.joinLayer()->getFeatures( request );
-        QgsFeature existingFeature;
-        it.nextFeature( existingFeature );
-
-        if ( existingFeature.isValid() )
-        {
-          const QStringList *subsetFields = info.joinFieldNamesSubset();
-          if ( subsetFields )
-          {
-            Q_FOREACH ( const QString &field, *subsetFields )
-              existingFeature.setAttribute( field, joinFeature.attribute( field ) );
-          }
-          else
-          {
-            Q_FOREACH ( const QgsField &field, joinFeature.fields() )
-              existingFeature.setAttribute( field.name(), joinFeature.attribute( field.name() ) );
-          }
-
-          joinLayer->updateFeature( existingFeature );
-        }
-        else
-        {
-          // joined feature is added only if one of its field is not null
-          bool notNullFields = false;
-          Q_FOREACH ( const QgsField &field, joinFeature.fields() )
-          {
-            if ( field.name() == info.joinFieldName() )
-              continue;
-
-            if ( !joinFeature.attribute( field.name() ).isNull() )
-            {
-              notNullFields = true;
-              break;
-            }
-          }
-
-          if ( notNullFields )
-            joinFeatures << joinFeature;
-        }
-      }
-
-      joinLayer->addFeatures( joinFeatures );
-    }
-  }
-
-  return true;
-}
-
 void QgsVectorLayer::setCoordinateSystem()
 {
   QgsDebugMsg( "----- Computing Coordinate System" );
diff --git a/src/core/qgsvectorlayer.h b/src/core/qgsvectorlayer.h
index 28fdc70b64df..69d1488bcd4b 100644
--- a/src/core/qgsvectorlayer.h
+++ b/src/core/qgsvectorlayer.h
@@ -1932,9 +1932,6 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
     //! Read simple labeling from layer's custom properties (QGIS 2.x projects)
     QgsAbstractVectorLayerLabeling *readLabelingFromCustomProperties();
 
-    bool addFeaturesToJoinedLayers( QgsFeatureList &features, Flags flags = 0 );
-    bool deleteFeaturesFromJoinedLayers( QgsFeatureIds fids );
-
 #ifdef SIP_RUN
     QgsVectorLayer( const QgsVectorLayer &rhs );
 #endif
diff --git a/src/core/qgsvectorlayerjoinbuffer.cpp b/src/core/qgsvectorlayerjoinbuffer.cpp
index 86ed5c154449..1f1d81348721 100644
--- a/src/core/qgsvectorlayerjoinbuffer.cpp
+++ b/src/core/qgsvectorlayerjoinbuffer.cpp
@@ -517,3 +517,137 @@ void QgsVectorLayerJoinBuffer::connectJoinedLayer( QgsVectorLayer *vl )
   connect( vl, &QgsVectorLayer::layerModified, this, &QgsVectorLayerJoinBuffer::joinedLayerModified, Qt::UniqueConnection );
   connect( vl, &QgsVectorLayer::willBeDeleted, this, &QgsVectorLayerJoinBuffer::joinedLayerWillBeDeleted, Qt::UniqueConnection );
 }
+
+bool QgsVectorLayerJoinBuffer::addFeature( const QgsFeature &feature ) const
+{
+  return addFeatures( QgsFeatureList() << feature );
+}
+
+bool QgsVectorLayerJoinBuffer::addFeatures( const QgsFeatureList &features ) const
+{
+  if ( !containsJoins() )
+    return false;
+
+  // try to add/update a feature in each joined layer
+  Q_FOREACH ( const QgsVectorLayerJoinInfo &info, vectorJoins() )
+  {
+    QgsVectorLayer *joinLayer = info.joinLayer();
+
+    if ( joinLayer && joinLayer->isEditable() && info.isEditable() && info.hasUpsertOnEdit() )
+    {
+      QgsFeatureList joinFeatures;
+
+      Q_FOREACH ( const QgsFeature &feature, features )
+      {
+        const QgsFeature joinFeature = info.extractJoinedFeature( feature );
+
+        // we don't want to add a new feature in joined layer when the id
+        // column value yet exist, we just want to update the existing one
+        const QVariant idFieldValue = feature.attribute( info.targetFieldName() );
+        const QString filter = QgsExpression::createFieldEqualityExpression( info.joinFieldName(), idFieldValue.toString() );
+
+        QgsFeatureRequest request;
+        request.setFilterExpression( filter );
+        request.setLimit( 1 );
+
+        QgsFeatureIterator it = info.joinLayer()->getFeatures( request );
+        QgsFeature existingFeature;
+        it.nextFeature( existingFeature );
+
+        if ( existingFeature.isValid() )
+        {
+          const QStringList *subsetFields = info.joinFieldNamesSubset();
+          if ( subsetFields )
+          {
+            Q_FOREACH ( const QString &field, *subsetFields )
+              existingFeature.setAttribute( field, joinFeature.attribute( field ) );
+          }
+          else
+          {
+            Q_FOREACH ( const QgsField &field, joinFeature.fields() )
+              existingFeature.setAttribute( field.name(), joinFeature.attribute( field.name() ) );
+          }
+
+          joinLayer->updateFeature( existingFeature );
+        }
+        else
+        {
+          // joined feature is added only if one of its field is not null
+          bool notNullFields = false;
+          Q_FOREACH ( const QgsField &field, joinFeature.fields() )
+          {
+            if ( field.name() == info.joinFieldName() )
+              continue;
+
+            if ( !joinFeature.attribute( field.name() ).isNull() )
+            {
+              notNullFields = true;
+              break;
+            }
+          }
+
+          if ( notNullFields )
+            joinFeatures << joinFeature;
+        }
+      }
+
+      joinLayer->addFeatures( joinFeatures );
+    }
+  }
+
+  return true;
+}
+
+bool QgsVectorLayerJoinBuffer::changeAttributeValue( QgsFeatureId fid, int field, const QVariant &newValue, const QVariant &oldValue ) const
+{
+  if ( mLayer->fields().fieldOrigin( field ) != QgsFields::OriginJoin )
+    return false;
+
+  int srcFieldIndex;
+  const QgsVectorLayerJoinInfo *info = joinForFieldIndex( field, mLayer->fields(), srcFieldIndex );
+  if ( info && info->joinLayer() && info->isEditable() )
+  {
+    QgsFeature feature = mLayer->getFeature( fid );
+
+    if ( !feature.isValid() )
+      return false;
+
+    const QgsFeature joinFeature = joinedFeatureOf( info, feature );
+
+    if ( joinFeature.isValid() )
+      return info->joinLayer()->changeAttributeValue( joinFeature.id(), srcFieldIndex, newValue, oldValue );
+    else
+    {
+      feature.setAttribute( field, newValue );
+      return addFeatures( QgsFeatureList() << feature );
+    }
+  }
+  else
+    return false;
+}
+
+bool QgsVectorLayerJoinBuffer::deleteFeature( QgsFeatureId fid ) const
+{
+  return deleteFeatures( QgsFeatureIds() << fid );
+}
+
+bool QgsVectorLayerJoinBuffer::deleteFeatures( const QgsFeatureIds &fids ) const
+{
+  if ( !containsJoins() )
+    return false;
+
+  Q_FOREACH ( const QgsFeatureId &fid, fids )
+  {
+    Q_FOREACH ( const QgsVectorLayerJoinInfo &info, vectorJoins() )
+    {
+      if ( info.isEditable() && info.hasCascadedDelete() )
+      {
+        const QgsFeature joinFeature = joinedFeatureOf( &info, mLayer->getFeature( fid ) );
+        if ( joinFeature.isValid() )
+          info.joinLayer()->deleteFeature( joinFeature.id() );
+      }
+    }
+  }
+
+  return true;
+}
diff --git a/src/core/qgsvectorlayerjoinbuffer.h b/src/core/qgsvectorlayerjoinbuffer.h
index 02ed58194a79..e38dcefe704d 100644
--- a/src/core/qgsvectorlayerjoinbuffer.h
+++ b/src/core/qgsvectorlayerjoinbuffer.h
@@ -109,6 +109,77 @@ class CORE_EXPORT QgsVectorLayerJoinBuffer : public QObject
     //! \since QGIS 2.6
     QgsVectorLayerJoinBuffer *clone() const SIP_FACTORY;
 
+    /**
+     * Adds a feature in joined layers. The feature given in parameter is the
+     * one added in target layer. If a corresponding joined feature yet exists
+     * in a joined layer, then this feature is just updated. Note that if a
+     * corresponding joined feature has only empty fields, then it's not
+     * created nor added.
+     *
+     * \param feature The feature added in the target layer.
+     *
+     * \returns false if an error happened, true otherwise
+     *
+     * \since QGIS 3.0
+     */
+    bool addFeature( const QgsFeature &feature ) const;
+
+    /**
+     * Adds a list of features in joined layers. Features given in parameter
+     * are those added in target layer. If a corresponding joined feature yet
+     * exists in a joined layer, then this feature is just updated. Note that
+     * if a corresponding joined feature has only empty fields, then it's not
+     * created nor added.
+     *
+     * \param features The list of features added in the target layer
+     *
+     * \returns false if an error happened, true otherwise
+     *
+     * \since QGIS 3.0
+     */
+    bool addFeatures( const QgsFeatureList &features ) const;
+
+    /**
+     * Changes attribute value in joined layers. The feature id given in
+     * parameter is the one added in target layer. If the corresponding joined
+     * feature does not exist in a joined layer, then it's automatically
+     * created if its fields are not empty.
+     *
+     * \param fid The feature id
+     * \param field The field to update
+     * \param newValue The new value of the attribute
+     * \param oldValue The old value of the attribute
+     *
+     * \returns false if an error happened, true otherwise
+     *
+     * \since QGIS 3.0
+     */
+    bool changeAttributeValue( QgsFeatureId fid, int field, const QVariant &newValue, const QVariant &oldValue = QVariant() ) const;
+
+    /**
+     * Deletes a feature from joined layers. The feature id given in
+     * parameter is the one coming from the target layer.
+     *
+     * \param fid The feature id from the target layer to delete
+     *
+     * \returns false if an error happened, true otherwise
+     *
+     * \since QGIS 3.0
+     */
+    bool deleteFeature( QgsFeatureId fid ) const;
+
+    /**
+     * Deletes a list of features from joined layers. Feature ids given
+     * in aprameter are those coming from the target layer.
+     *
+     * \param fids Feature ids from the target layer to delete
+     *
+     * \returns false if an error happened, true otherwise
+     *
+     * \since QGIS 3.0
+     */
+    bool deleteFeatures( const QgsFeatureIds &fids ) const;
+
   signals:
     //! Emitted whenever the list of joined fields changes (e.g. added join or joined layer's fields change)
     //! \since QGIS 2.6