Add optimistic locking column to ci_stages table

db/migrate/20170720111708_add_lock_version_to_ci_stages.rb

+class AddLockVersionToCiStages < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def change
+    add_column :ci_stages, :lock_version, :integer
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170717150329) do
+ActiveRecord::Schema.define(version: 20170720111708) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -366,6 +366,7 @@ ActiveRecord::Schema.define(version: 20170717150329) do
     t.datetime "updated_at"
     t.string "name"
     t.integer "status"
+    t.integer "lock_version"
   end
 
   add_index "ci_stages", ["pipeline_id", "name"], name: "index_ci_stages_on_pipeline_id_and_name", using: :btree