Do not load all projects all the time.

app/services/filtering_service.rb

@@ -24,10 +24,10 @@ class FilteringService
     @current_user = current_user
     @params = params
 
-    items = by_scope
+    items = init_collection
+    items = by_scope(items)
     items = by_state(items)
     items = by_group(items)
-    items = by_project(items)
     items = by_search(items)
     items = by_milestone(items)
     items = by_assignee(items)
@@ -37,24 +37,30 @@ class FilteringService
 
   private
 
-  def by_scope
+  def init_collection
     table_name = klass.table_name
 
-    case params[:scope]
-    when 'created-by-me', 'authored' then
-      current_user.send(table_name)
-    when 'all' then
-      if current_user
-        if project && (project.public? || project.internal?)
-          klass.of_projects(Project.public_or_internal_only(current_user))
+    return klass.of_projects(Project.public_only) unless current_user
+
+    if project
+      if current_user.can?(:read_project, project)
+        project.send(table_name)
       else
-          klass.of_projects(current_user.authorized_projects.pluck(:id))
+        []
       end
     else
-        klass.of_projects(Project.public_only)
+      klass.of_projects(current_user.authorized_projects)
+    end
   end
+
+  def by_scope(items)
+    case params[:scope]
+    when 'created-by-me', 'authored' then
+      klass.where(author_id: current_user.id)
+    when 'all' then
+      klass
     when 'assigned-to-me' then
-      current_user.send("assigned_#{table_name}")
+      klass.where(assignee_id: current_user.id)
     else
       raise 'You must specify default scope'
     end