Use cheaper .exists() instead of .count() for has_exercise filter
Use cheaper .exists() instead of .count() for has_exercise filter

benjaoming/kolibri,DXCanas/kolibri,benjaoming/kolibri,indirectlylit/kolibri,learningequality/kolibri,DXCanas/kolibri,lyw07/kolibri,lyw07/kolibri,learningequality/kolibri,mrpau/kolibri,learningequality/kolibri,mrpau/kolibri,indirectlylit/kolibri,indirectlylit/kolibri,jonboiser/kolibri,jonboiser/kolibri,jonboiser/kolibri,indirectlylit/kolibri,benjaoming/kolibri,benjaoming/kolibri,mrpau/kolibri,learningequality/kolibri,DXCanas/kolibri,mrpau/kolibri,lyw07/kolibri,DXCanas/kolibri,lyw07/kolibri,jonboiser/kolibri