prevent evaluation duplication

app/models/evaluation.rb

@@ -5,6 +5,7 @@
 #  id                   :bigint           not null, primary key
 #  entry_request_status :string(255)
 #  explanation          :text
+#  idx_in_semester      :integer          default(0), not null
 #  is_considered        :boolean          default(FALSE), not null
 #  justification        :text             not null
 #  last_evaulation      :datetime
@@ -21,9 +22,10 @@
 #
 # Indexes
 #
-#  ert_semester_idx  (semester)
-#  next_version_idx  (next_version)
-#  unique_idx        (group_id,semester,next_version NULLS FIRST) UNIQUE
+#  ert_semester_idx                                                (semester)
+#  index_evaluations_on_group_id_and_semester_and_idx_in_semester  (group_id,semester,idx_in_semester) UNIQUE
+#  next_version_idx                                                (next_version)
+#  unique_idx                                                      (group_id,semester,next_version NULLS FIRST) UNIQUE
 #
 # Foreign Keys
 #

db/migrate/20240707094123_add_unique_index_on_evaluation_semester.rb

@@ -0,0 +1,23 @@
+class AddUniqueIndexOnEvaluationSemester < ActiveRecord::Migration[6.0]
+  # We have multiple evaluations for the same group in the same semester from previous years,
+  # this prevents us from using a unique index on [:group_id, :semester].
+  # The idx_in_semester columns solves this by setting an arbitrary value where duplication is present and
+  # 0 for cases with no duplication.'
+  def up
+    add_column :evaluations, :idx_in_semester, :integer, default: 0, null: false
+
+    evaluation_groups = Evaluation.all.group_by { |evaluation| [evaluation.group_id, evaluation.semester] }
+    evaluation_groups.each do |id, evaluations|
+      evaluations.each.with_index do |evaluation, index|
+        evaluation.update!(idx_in_semester: index)
+      end
+    end
+
+    add_index :evaluations, [:group_id, :semester, :idx_in_semester], unique: true
+  end
+
+  def down
+    remove_index :evaluations, column: [:group_id, :semester, :idx_in_semester]
+    remove_column :evaluations, :idx_in_semester
+  end
+end

db/structure.sql

@@ -134,7 +134,8 @@ CREATE TABLE public.evaluations (
     next_version bigint,
     explanation text,
     optlock integer DEFAULT 0 NOT NULL,
-    is_considered boolean DEFAULT false NOT NULL
+    is_considered boolean DEFAULT false NOT NULL,
+    idx_in_semester integer DEFAULT 0 NOT NULL
 );
 
 
@@ -1248,6 +1249,13 @@ CREATE INDEX idx_groups_grp_type ON public.groups USING btree (grp_type);
 CREATE UNIQUE INDEX index_entry_requests_on_evaluation_id_and_user_id ON public.entry_requests USING btree (evaluation_id, user_id);
 
 
+--
+-- Name: index_evaluations_on_group_id_and_semester_and_idx_in_semester; Type: INDEX; Schema: public; Owner: -
+--
+
+CREATE UNIQUE INDEX index_evaluations_on_group_id_and_semester_and_idx_in_semester ON public.evaluations USING btree (group_id, semester, idx_in_semester);
+
+
 --
 -- Name: index_notifications_on_group_owner_id; Type: INDEX; Schema: public; Owner: -
 --
@@ -1754,6 +1762,7 @@ INSERT INTO "schema_migrations" (version) VALUES
 ('20221206081834'),
 ('20221209072919'),
 ('20221209100356'),
-('20240419155504');
+('20240419155504'),
+('20240707094123');
 
 

spec/requests/evalutations_controller_spec.rb

@@ -159,7 +159,7 @@
 
     before(:each) do
       evaluation.update!(id:2)
-      previous_evaluation = create(:evaluation, group: group, id: 1 )
+      previous_evaluation = create(:evaluation, group: group, id: 1, semester: '201720182')
       Principle.create!(evaluation: previous_evaluation,
                         name: 'Previous principle',
                         type: Principle::WORK,