Project: QGIS
Version: 2.14.0
QgsFeatureRequest now supports settings a maximum limit for the number of features returned. In many cases this limit is passed to the provider, resulting in significant performance gains when only a set number of features are required.
Additionally, QgsFeatureRequest now supports setting ordering for returned features. Again, in many cases this ordering is delegated to the provider so that it is performed "server side" for optimal performance.
