add index on notification settings columns expected to have be distributed unevenly

db/migrate/20210802114054_add_notification_setting_options.rb

@@ -2,16 +2,19 @@ class AddNotificationSettingOptions < ActiveRecord::Migration[6.1]
   def change
     add_notification_settings_options
     update_notified_events
-
-    # TODO: add index to all boolean fields
   end
 
   def add_notification_settings_options
     change_table :notification_settings, bulk: true do |t|
-      t.boolean :work_package_commented, default: false
-      t.boolean :work_package_created, default: false
-      t.boolean :work_package_processed, default: false
-      t.boolean :work_package_prioritized, default: false
+      # Adding indices here is probably useful as most of those are expected to be false
+      # and we are searching for those that are true.
+      # The columns watched, involved and mentioned will probably be true most of the time
+      # so having an index there should not improve speed.
+      t.boolean :work_package_commented, default: false, index: true
+      t.boolean :work_package_created, default: false, index: true
+      t.boolean :work_package_processed, default: false, index: true
+      t.boolean :work_package_prioritized, default: false, index: true
+      t.index :all
     end
   end