Iterations - constraint date ranges do not overlap

Adds btree_gist postgresql extension.
Makes it so that Iterations inside the same group/project cannot have
overlapping date ranges.

changelogs/unreleased/iterations_add_daterange_constraint-unrevert.yml

+---
+title: Add btree_gist PGSQL extension and add DB constraints for Iteration date ranges
+merge_request: 33340
+author:
+type: added

db/migrate/20200515152649_enable_btree_gist_extension.rb

+# frozen_string_literal: true
+
+class EnableBtreeGistExtension < ActiveRecord::Migration[6.0]
+  DOWNTIME = false
+
+  def up
+    execute 'CREATE EXTENSION IF NOT EXISTS btree_gist'
+  end
+
+  def down
+    execute 'DROP EXTENSION IF EXISTS btree_gist'
+  end
+end

db/migrate/20200515153633_iteration_date_range_constraint.rb

+# frozen_string_literal: true
+
+class IterationDateRangeConstraint < ActiveRecord::Migration[6.0]
+  DOWNTIME = false
+
+  def up
+    execute <<~SQL
+      ALTER TABLE sprints
+        ADD CONSTRAINT iteration_start_and_due_daterange_project_id_constraint
+        EXCLUDE USING gist
+        ( project_id WITH =,
+          daterange(start_date, due_date, '[]') WITH &&
+        )
+        WHERE (project_id IS NOT NULL)
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE sprints
+        ADD CONSTRAINT iteration_start_and_due_daterange_group_id_constraint
+        EXCLUDE USING gist
+        ( group_id WITH =,
+          daterange(start_date, due_date, '[]') WITH &&
+        )
+        WHERE (group_id IS NOT NULL)
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      ALTER TABLE sprints
+        DROP CONSTRAINT IF EXISTS iteration_start_and_due_daterange_project_id_constraint
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE sprints
+        DROP CONSTRAINT IF EXISTS iteration_start_and_due_daterange_group_id_constraint
+    SQL
+  end
+end

db/structure.sql

@@ -8,6 +8,8 @@ CREATE SCHEMA gitlab_partitions_static;
 
 COMMENT ON SCHEMA gitlab_partitions_static IS 'Schema to hold static partitions, e.g. for hash partitioning';
 
+CREATE EXTENSION IF NOT EXISTS btree_gist WITH SCHEMA public;
+
 CREATE EXTENSION IF NOT EXISTS pg_trgm WITH SCHEMA public;
 
 CREATE TABLE public.product_analytics_events_experimental (
@@ -17809,6 +17811,12 @@ ALTER TABLE ONLY public.issue_user_mentions
 ALTER TABLE ONLY public.issues
     ADD CONSTRAINT issues_pkey PRIMARY KEY (id);
 
+ALTER TABLE ONLY public.sprints
+    ADD CONSTRAINT iteration_start_and_due_daterange_group_id_constraint EXCLUDE USING gist (group_id WITH =, daterange(start_date, due_date, '[]'::text) WITH &&) WHERE ((group_id IS NOT NULL));
+
+ALTER TABLE ONLY public.sprints
+    ADD CONSTRAINT iteration_start_and_due_daterange_project_id_constraint EXCLUDE USING gist (project_id WITH =, daterange(start_date, due_date, '[]'::text) WITH &&) WHERE ((project_id IS NOT NULL));
+
 ALTER TABLE ONLY public.jira_connect_installations
     ADD CONSTRAINT jira_connect_installations_pkey PRIMARY KEY (id);
 
@@ -23691,6 +23699,8 @@ COPY "schema_migrations" (version) FROM STDIN;
 20200514000009
 20200514000132
 20200514000340
+20200515152649
+20200515153633
 20200515155620
 20200518091745
 20200518114540

spec/models/iteration_spec.rb

@@ -54,7 +54,10 @@ RSpec.describe Iteration do
       end
 
       context 'when dates overlap' do
-        context 'same group' do
+        let(:start_date) { 5.days.from_now }
+        let(:due_date) { 6.days.from_now }
+
+        shared_examples_for 'overlapping dates' do
           context 'when start_date is in range' do
             let(:start_date) { 5.days.from_now }
             let(:due_date) { 3.weeks.from_now }
@@ -63,6 +66,11 @@ RSpec.describe Iteration do
               expect(subject).not_to be_valid
               expect(subject.errors[:base]).to include('Dates cannot overlap with other existing Iterations')
             end
+
+            it 'is not valid even if forced' do
+              subject.validate # to generate iid/etc
+              expect { subject.save!(validate: false) }.to raise_exception(ActiveRecord::StatementInvalid, /#{constraint_name}/)
+            end
           end
 
           context 'when end_date is in range' do
@@ -73,25 +81,84 @@ RSpec.describe Iteration do
               expect(subject).not_to be_valid
               expect(subject.errors[:base]).to include('Dates cannot overlap with other existing Iterations')
             end
+
+            it 'is not valid even if forced' do
+              subject.validate # to generate iid/etc
+              expect { subject.save!(validate: false) }.to raise_exception(ActiveRecord::StatementInvalid, /#{constraint_name}/)
+            end
           end
 
           context 'when both overlap' do
-            let(:start_date) { 5.days.from_now }
-            let(:due_date) { 6.days.from_now }
-
             it 'is not valid' do
               expect(subject).not_to be_valid
               expect(subject.errors[:base]).to include('Dates cannot overlap with other existing Iterations')
             end
+
+            it 'is not valid even if forced' do
+              subject.validate # to generate iid/etc
+              expect { subject.save!(validate: false) }.to raise_exception(ActiveRecord::StatementInvalid, /#{constraint_name}/)
+            end
           end
         end
 
-        context 'different group' do
-          let(:start_date) { 5.days.from_now }
-          let(:due_date) { 6.days.from_now }
-          let(:group) { create(:group) }
+        context 'group' do
+          it_behaves_like 'overlapping dates' do
+            let(:constraint_name) { 'iteration_start_and_due_daterange_group_id_constraint' }
+          end
+
+          context 'different group' do
+            let(:group) { create(:group) }
+
+            it { is_expected.to be_valid }
+
+            it 'does not trigger exclusion constraints' do
+              expect { subject.save! }.not_to raise_exception
+            end
+          end
+
+          context 'in a project' do
+            let(:project) { create(:project) }
+
+            subject { build(:iteration, project: project, start_date: start_date, due_date: due_date) }
+
+            it { is_expected.to be_valid }
 
-          it { is_expected.to be_valid }
+            it 'does not trigger exclusion constraints' do
+              expect { subject.save! }.not_to raise_exception
+            end
+          end
+        end
+
+        context 'project' do
+          let_it_be(:existing_iteration) { create(:iteration, project: project, start_date: 4.days.from_now, due_date: 1.week.from_now) }
+
+          subject { build(:iteration, project: project, start_date: start_date, due_date: due_date) }
+
+          it_behaves_like 'overlapping dates' do
+            let(:constraint_name) { 'iteration_start_and_due_daterange_project_id_constraint' }
+          end
+
+          context 'different project' do
+            let(:project) { create(:project) }
+
+            it { is_expected.to be_valid }
+
+            it 'does not trigger exclusion constraints' do
+              expect { subject.save! }.not_to raise_exception
+            end
+          end
+
+          context 'in a group' do
+            let(:group) { create(:group) }
+
+            subject { build(:iteration, group: group, start_date: start_date, due_date: due_date) }
+
+            it { is_expected.to be_valid }
+
+            it 'does not trigger exclusion constraints' do
+              expect { subject.save! }.not_to raise_exception
+            end
+          end
         end
       end
     end