ruby - SQLite3::SQLException: duplicate column name: User_id: ALTER TABLE "comments" ADD "User_id" integer/ -

i ran command

rails g migration adduser_idtocomments user_id:string

and figured out user_id should integer , ran

rails g migration adduser_idtocomments user_id:integer --force thinking overwrite initial command.

but now, i'm getting error:

``` louismorin$ rake db:migrate == 20140910155248 addindextocomments: migrating =============================== -- add_column(:comments, :index, :string) -> 0.0069s == 20140910155248 addindextocomments: migrated (0.0070s) ======================

== 20140910181022 adduseridtocomments: migrating ============================== -- add_column(:comments, :user_id, :integer) rake aborted! standarderror: error has occurred, , later migrations canceled:

sqlite3::sqlexception: duplicate column name: user_id: alter table "comments" add "user_id" integer/users/louismorin/code/cp299/db/migrate/20140910181022_add_user_id_to_comments.rb:3:in change' activerecord::statementinvalid: sqlite3::sqlexception: duplicate column name: user_id: alter table "comments" add "user_id" integer /users/louismorin/code/cp299/db/migrate/20140910181022_add_user_id_to_comments.rb:3:inchange' sqlite3::sqlexception: duplicate column name: user_id /users/louismorin/code/cp299/db/migrate/20140910181022_add_user_id_to_comments.rb:3:in `change' tasks: top => db:migrate (see full trace running task --trace) ```

here's schema.rb file

``` activerecord::schema.define(version: 20140910155210) do

create_table "comments", force: true |t|   t.text     "body"   t.integer  "post_id"   t.datetime "created_at"   t.datetime "updated_at"   t.string   "user_id" end  add_index "comments", ["post_id"], name: "index_comments_on_post_id"  create_table "posts", force: true |t|   t.string   "title"   t.text     "body"   t.datetime "created_at"   t.datetime "updated_at"   t.integer  "user_id"   t.integer  "topic_id" end  add_index "posts", ["topic_id"], name: "index_posts_on_topic_id" add_index "posts", ["user_id"], name: "index_posts_on_user_id"  create_table "topics", force: true |t|   t.string   "name"   t.boolean  "public",      default: true   t.text     "description"   t.datetime "created_at"   t.datetime "updated_at" end  create_table "users", force: true |t|   t.string   "email",                  default: "", null: false   t.string   "encrypted_password",     default: "", null: false   t.string   "reset_password_token"   t.datetime "reset_password_sent_at"   t.datetime "remember_created_at"   t.integer  "sign_in_count",          default: 0,  null: false   t.datetime "current_sign_in_at"   t.datetime "last_sign_in_at"   t.string   "current_sign_in_ip"   t.string   "last_sign_in_ip"   t.string   "confirmation_token"   t.datetime "confirmed_at"   t.datetime "confirmation_sent_at"   t.string   "unconfirmed_email"   t.string   "name"   t.datetime "created_at"   t.datetime "updated_at"   t.string   "role"   t.string   "avatar"   t.string   "image" end  add_index "users", ["email"], name: "index_users_on_email", unique: true add_index "users", ["reset_password_token"], name: "index_users_on_reset_password_token", unique:     true  end 

```

because of error, second migration -- changing column type -- didn't run. if migration intended change 1 column, delete file generated , try again.

if don't yet have data in column care about, that's pretty easy:

rails g migration changetypeofuseridoncomments

this migration name isn't special. might have been dowhateveriwant

then, edit created migration's change method this:

def change   remove_column :comments, :user_id   add_column :comments, :user_id, :integer   add_index :comments, :user_id end 

when run un-run migrations rake db:migrate, shouldn't trip on 1 errored (because deleted it), , should run one, removes column , adds correct type.

if have data want save, procedure more complicated. change method have grab current user_id's each comment, , assign them new comments when create new column. below should work:

def change   user_ids = {}   comment.find_each{ |c| user_ids[c.id] = c.user_id.to_i }     remove_column :comments, :user_id   add_column :comments, :user_id, :integer   add_index :comments, :user_id   comment.each{ |c| c.update_attribute(:user_id, user_ids[c.id]) end 

also note names of migration in command camelcase or snake_case. so: addcolumnuseridtocomments or add_column_user_id_to_comments. naming did might cause problems.

** edit **

modify column's type in sqlite3

it appears sqlite has no way modify/drop column. i'd suggest either:

dropping , restarting sqlite table

drop table, drop original user_id migration , line in new 1 removing old user_id column, , create new table new migrations. should work fine if don't care data

switching postgres, database heroku uses.

it's idea (because want production , local databases behave identically), can bug-prone switch to.

look here guidance -- change sqlite postgresql in fresh rails project