Add version column to operations feature flags table

Default to 1 and do not allow null values
Allow version to equal 1 or 2 with model validations

changelogs/unreleased/add-feature-flags-version.yml

+---
+title: Add version column to operations_feature_flags table
+merge_request: 25552
+author:
+type: added

db/migrate/20200224163804_add_version_to_feature_flags_table.rb

+# frozen_string_literal: true
+
+class AddVersionToFeatureFlagsTable < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  FEATURE_FLAG_LEGACY_VERSION = 1
+
+  def up
+    # The operations_feature_flags table is small enough that we can disable this cop.
+    # See https://gitlab.com/gitlab-org/gitlab/-/merge_requests/25552#note_291202882
+    # rubocop: disable Migration/AddColumnWithDefault
+    add_column_with_default(:operations_feature_flags, :version, :smallint, default: FEATURE_FLAG_LEGACY_VERSION, allow_null: false)
+    # rubocop: enable Migration/AddColumnWithDefault
+  end
+
+  def down
+    remove_column(:operations_feature_flags, :version)
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_02_21_144534) do
+ActiveRecord::Schema.define(version: 2020_02_24_163804) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_trgm"
@@ -2916,6 +2916,7 @@ ActiveRecord::Schema.define(version: 2020_02_21_144534) do
     t.string "name", null: false
     t.text "description"
     t.integer "iid", null: false
+    t.integer "version", limit: 2, default: 1, null: false
     t.index ["project_id", "iid"], name: "index_operations_feature_flags_on_project_id_and_iid", unique: true
     t.index ["project_id", "name"], name: "index_operations_feature_flags_on_project_id_and_name", unique: true
   end

ee/app/models/operations/feature_flag.rb

@@ -25,6 +25,7 @@ module Operations
       }
     validates :name, uniqueness: { scope: :project_id }
     validates :description, allow_blank: true, length: 0..255
+    validates :version, inclusion: { in: [1, 2], message: 'must be 1 or 2' }
     validate :first_default_scope, on: :create, if: :has_scopes?
 
     before_create :build_default_scope, unless: :has_scopes?

ee/spec/models/operations/feature_flag_spec.rb

@@ -16,6 +16,7 @@ describe Operations::FeatureFlag do
     it { is_expected.to validate_presence_of(:project) }
     it { is_expected.to validate_presence_of(:name) }
     it { is_expected.to validate_uniqueness_of(:name).scoped_to(:project_id) }
+    it { is_expected.to validate_inclusion_of(:version).in_array([1, 2]).with_message('must be 1 or 2') }
 
     it_behaves_like 'AtomicInternalId', validate_presence: false do
       let(:internal_id_attribute) { :iid }
@@ -26,6 +27,17 @@ describe Operations::FeatureFlag do
     end
   end
 
+  describe 'feature flag version' do
+    it 'defaults to 1 if unspecified' do
+      project = create(:project)
+
+      feature_flag = described_class.create(name: 'my_flag', project: project, active: true)
+
+      expect(feature_flag).to be_valid
+      expect(feature_flag.version).to eq(1)
+    end
+  end
+
   describe 'Scope creation' do
     subject { described_class.new(**params) }