optimize work package fetching for scheduling

app/models/work_packages/scopes/for_scheduling.rb

@@ -118,26 +118,29 @@ module WorkPackages::Scopes
       def scheduling_paths_sql(work_packages)
         values = work_packages.map do |wp|
           ::OpenProject::SqlSanitization
-            .sanitize "(:id, false)",
+            .sanitize "(:id, false, false)",
                       id: wp.id
         end.join(', ')
 
         <<~SQL.squish
           to_schedule (id, manually) AS (
-            SELECT * FROM (VALUES#{values}) AS t(id, manually)
+
+            SELECT * FROM (VALUES#{values}) AS t(id, manually, hierarchy_up)
 
             UNION
 
             SELECT
               relations.from_id id,
-              (related_work_packages.schedule_manually OR COALESCE(descendants.manually, false)) manually
+              (related_work_packages.schedule_manually OR COALESCE(descendants.manually, false)) manually,
+              relations.hierarchy_up
             FROM
               to_schedule
             JOIN LATERAL
               (
                 SELECT
                   from_id,
-                  to_id
+                  to_id,
+                  false hierarchy_up
                 FROM
                   relations
                 WHERE NOT to_schedule.manually
@@ -149,14 +152,14 @@ module WorkPackages::Scopes
                     THEN work_package_hierarchies.descendant_id
                     ELSE work_package_hierarchies.ancestor_id
                     END from_id,
-                  to_schedule.id to_id
+                  to_schedule.id to_id,
+                  work_package_hierarchies.descendant_id = to_schedule.id hierarchy_up
                 FROM
                   work_package_hierarchies
                 WHERE
                   NOT to_schedule.manually
-                  AND work_package_hierarchies.generations = 1
-                  AND (work_package_hierarchies.ancestor_id = to_schedule.id
-                       OR work_package_hierarchies.descendant_id = to_schedule.id)
+                  AND ((work_package_hierarchies.ancestor_id = to_schedule.id AND NOT to_schedule.hierarchy_up AND work_package_hierarchies.generations = 1)
+                       OR (work_package_hierarchies.descendant_id = to_schedule.id AND work_package_hierarchies.generations > 0))
               ) relations ON relations.to_id = to_schedule.id
             LEFT JOIN work_packages related_work_packages
               ON relations.from_id = related_work_packages.id

app/services/work_packages/schedule_dependency.rb

@@ -59,24 +59,23 @@ class WorkPackages::ScheduleDependency
   private
 
   def build_dependencies
-    following = load_following(work_packages)
+    following = load_following
 
     # Those variables are pure optimizations.
     # We want to reuse the already loaded work packages as much as possible
     # and we want to have them readily available as hashes.
     self.known_work_packages += following
     known_work_packages.uniq!
-    self.known_work_packages_by_id = known_work_packages.group_by(&:id)
-    self.known_work_packages_by_parent_id = known_work_packages.group_by(&:parent_id)
+    self.known_work_packages_by_id = known_work_packages.group_by(&:id).transform_values(&:first)
+    self.known_work_packages_by_parent_id = fetch_descendants.group_by(&:parent_id)
 
     add_dependencies(following)
   end
 
-  def load_following(work_packages)
+  def load_following
     WorkPackage
       .for_scheduling(work_packages)
-      .includes(:parent,
-                follows_relations: :to)
+      .includes(follows_relations: :to)
   end
 
   def add_dependencies(dependent_work_packages)
@@ -127,6 +126,19 @@ class WorkPackages::ScheduleDependency
     end
   end
 
+  # Use a mixture of work packages that are already loaded to be scheduled themselves but also load
+  # all the rest of the descendants. There are two cases in which descendants are not loaded for scheduling:
+  # * manual scheduling: A descendant is either scheduled manually itself or all of its descendants are scheduled manually.
+  # * sibling: the descendant is not below a work package to be scheduled (e.g. one following another) but below an ancestor of
+  #            a schedule work package.
+  def fetch_descendants
+    descendants = known_work_packages_by_id.values
+
+    descendants + WorkPackage
+                    .with_ancestor(descendants)
+                    .where.not(id: known_work_packages_by_id.keys)
+  end
+
   class Dependency
     def initialize(work_package, schedule_dependency)
       self.schedule_dependency = schedule_dependency
@@ -195,7 +207,7 @@ class WorkPackages::ScheduleDependency
         parent = known_work_packages_by_id[work_package.parent_id]
 
         if parent
-          parent + ancestors_from_preloaded(parent.first)
+          [parent] + ancestors_from_preloaded(parent)
         end
       end || []
     end

spec/models/work_packages/scopes/for_scheduling_spec.rb

@@ -503,6 +503,22 @@ describe WorkPackages::Scopes::ForScheduling, 'allowed scope' do
         end
       end
     end
+
+    context 'for a work package with a sibling and a successor that also has a sibling' do
+      let(:sibling) do
+        create(:work_package, project: project, parent: parent)
+      end
+      let(:successor_sibling) do
+        create(:work_package, project: project, parent: successor_parent)
+      end
+
+      let!(:existing_work_packages) { [parent, sibling, successor, successor_parent, successor_sibling] }
+
+      it 'contains the successor and the parents but not the siblings' do
+        expect(WorkPackage.for_scheduling([origin]))
+          .to match_array([successor, parent, successor_parent])
+      end
+    end
   end
 end
 # rubocop:enable RSpec/MultipleMemoizedHelpers