Make commit and design user mention indexes unique

This is needed for the UPSERT to work properly since we're detecting a
unique constraint conflict on [noteable_id, note_id]

Changelog: other

app/models/alert_management/alert.rb

@@ -9,6 +9,7 @@ module AlertManagement
     include ShaAttribute
     include Sortable
     include Noteable
+    include Mentionable
     include Gitlab::SQL::Pattern
     include Presentable
     include Gitlab::Utils::StrongMemoize

db/migrate/20210818055357_add_unique_commit_design_user_mention_indexes.rb

+# frozen_string_literal: true
+
+class AddUniqueCommitDesignUserMentionIndexes < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  COMMIT_INDEX_NAME = 'commit_id_and_note_id_index'
+  DESIGN_INDEX_NAME = 'design_user_mentions_on_design_id_and_note_id_index'
+
+  COMMIT_UNIQUE_INDEX_NAME = 'commit_user_mentions_on_commit_id_and_note_id_unique_index'
+  DESIGN_UNIQUE_INDEX_NAME = 'design_user_mentions_on_design_id_and_note_id_unique_index'
+
+  def up
+    add_concurrent_index :commit_user_mentions, [:commit_id, :note_id], unique: true, name: COMMIT_UNIQUE_INDEX_NAME
+    add_concurrent_index :design_user_mentions, [:design_id, :note_id], unique: true, name: DESIGN_UNIQUE_INDEX_NAME
+
+    remove_concurrent_index_by_name :commit_user_mentions, COMMIT_INDEX_NAME
+    remove_concurrent_index_by_name :design_user_mentions, DESIGN_INDEX_NAME
+  end
+
+  def down
+    add_concurrent_index :design_user_mentions, [:design_id, :note_id], name: DESIGN_INDEX_NAME
+    add_concurrent_index :commit_user_mentions, [:commit_id, :note_id], name: COMMIT_INDEX_NAME
+
+    remove_concurrent_index_by_name :design_user_mentions, DESIGN_UNIQUE_INDEX_NAME
+    remove_concurrent_index_by_name :commit_user_mentions, COMMIT_UNIQUE_INDEX_NAME
+  end
+end

db/schema_migrations/20210818055357

+1092a16d742b08ef2ef5f74bdaa92bb5f9cedbdb1161ab71abe501c39b164689
\ No newline at end of file

db/structure.sql

@@ -22895,7 +22895,7 @@ CREATE INDEX ci_builds_gitlab_monitor_metrics ON ci_builds USING btree (status,
 
 CREATE INDEX code_owner_approval_required ON protected_branches USING btree (project_id, code_owner_approval_required) WHERE (code_owner_approval_required = true);
 
-CREATE INDEX commit_id_and_note_id_index ON commit_user_mentions USING btree (commit_id, note_id);
+CREATE UNIQUE INDEX commit_user_mentions_on_commit_id_and_note_id_unique_index ON commit_user_mentions USING btree (commit_id, note_id);
 
 CREATE INDEX composer_cache_files_index_on_deleted_at ON packages_composer_cache_files USING btree (delete_at, id);
 
@@ -22905,7 +22905,7 @@ CREATE UNIQUE INDEX dast_site_profiles_builds_on_ci_build_id ON dast_site_profil
 
 CREATE UNIQUE INDEX design_management_designs_versions_uniqueness ON design_management_designs_versions USING btree (design_id, version_id);
 
-CREATE INDEX design_user_mentions_on_design_id_and_note_id_index ON design_user_mentions USING btree (design_id, note_id);
+CREATE UNIQUE INDEX design_user_mentions_on_design_id_and_note_id_unique_index ON design_user_mentions USING btree (design_id, note_id);
 
 CREATE UNIQUE INDEX epic_user_mentions_on_epic_id_and_note_id_index ON epic_user_mentions USING btree (epic_id, note_id);
 

ee/app/models/ee/vulnerability.rb

@@ -10,6 +10,7 @@ module EE
       include ::Redactable
       include ::StripAttribute
       include ::Noteable
+      include ::Mentionable
       include ::Awardable
       include ::Referable
       include ::Presentable