Ruby on Rails migration stuck -

i'm new ruby on rails , grateful migrations. version 4

first migration

class createrooms < activerecord::migration   def change     create_table :rooms |t|       t.integer :legacy_id, null: true       t.string :tag, null: false       t.string :name_en, null: false       t.string :name_et, null: false       t.string :name_ru, null: false       t.string :color, default: 'black'       t.timestamp :enabled_from, default: 0       t.timestamp :enabled_to, default: 0       t.timestamps null: false      end     add_index :rooms, :tag, unique: true     add_index :rooms, :name_en, unique: true     add_index :rooms, :name_et, unique: true     add_index :rooms, :name_ru, unique: true    end end 

next one

class adddefaultvaluestoroom < activerecord::migration   def change     add_column :rooms, :priority, :integer, null: false     change_column :rooms, :enabled_from, :datetime, default: '2008-08-15'     change_column :rooms, :enabled_to, :datetime, default: '2050-12-31'     add_index :rooms, :priority, unique: true   end end 

strangely enough not reflected in schema

  create_table "rooms", force: :cascade |t|     t.integer  "legacy_id"     t.string   "tag",                                          null: false     t.string   "name_en",                                      null: false     t.string   "name_et",                                      null: false     t.string   "name_ru",                                      null: false     t.string   "color",        default: "black"     t.datetime "enabled_from", default: '2008-08-15 00:00:00'     t.datetime "enabled_to",   default: '2050-12-31 00:00:00'     t.datetime "created_at",                                   null: false     t.datetime "updated_at",                                   null: false   end    add_index "rooms", ["name_en"], name: "index_rooms_on_name_en", unique: true   add_index "rooms", ["name_et"], name: "index_rooms_on_name_et", unique: true   add_index "rooms", ["name_ru"], name: "index_rooms_on_name_ru", unique: true   add_index "rooms", ["tag"], name: "index_rooms_on_tag", unique: true 

rake db:rollback crashes

 rake db:rollback step=2 --trace ** invoke db:rollback (first_time) ** invoke environment (first_time) ** execute environment ** invoke db:load_config (first_time) ** execute db:load_config ** execute db:rollback   activerecord::schemamigration load (0.2ms)  select "schema_migrations".* "schema_migrations"   activerecord::schemamigration load (0.2ms)  select "schema_migrations".* "schema_migrations" migrating adddefaultvaluestoroom (20160127121254)    (0.1ms)  begin transaction == 20160127121254 adddefaultvaluestoroom: reverting ===========================    (0.1ms)  rollback transaction rake aborted! standarderror: error has occurred, , later migrations canceled:  activerecord::irreversiblemigration/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.2/lib/active_record/migration/command_recorder.rb:65:in `inverse_of' 

now i'm in fix, me out ?

tia pavel

change_column creates irreversible change database, means can't roll back. see guide: http://guides.rubyonrails.org/active_record_migrations.html#changing-columns

the idea here reverting data result in data loss, rails prevents doing destructive default , throws error stop process.

change last migration utilize reversible or up/down methods, in order explicitly tell rails how reverse change (note lose data stored in new column priority). see: http://guides.rubyonrails.org/active_record_migrations.html#using-reversible

here's example using up/down methods:

class adddefaultvaluestoroom < activerecord::migration   def     add_column :rooms, :priority, :integer, null: false     change_column :rooms, :enabled_from, :datetime, default: '2008-08-15'     change_column :rooms, :enabled_to, :datetime, default: '2050-12-31'     add_index :rooms, :priority, unique: true   end    def down     remove_column :rooms, :priority     change_column :rooms, :enabled_from, :datetime, default: 0     change_column :rooms, :enabled_to, :datetime, default: 0   end end