Devise rake db:migrate fails because of duplicate column in my User's table - Rails 3.1

This is the error I get when I am first installing Devise and running rake db:migrate:

==  AddDeviseToUsers: migrating ===============================================
-- change_table(:users)
rake aborted!
An error has occurred, this and all later migrations canceled:

SQLite3::SQLException: duplicate column name: email: ALTER TABLE "users" ADD "email" varchar(255) DEFAULT '' NOT NULL

Given that this is just test data, I could just delete that column in my db and re-run it, but that doesn't seem very Railsy - if only for the reason that it will making my staging server (the only other server with my app) out-of-sync with my localhost.

Also, what if there is a conflict with another column.

So given that this is the schema of my User table before running开发者_运维问答 the migration, how should I handle this? With a migration of some sort that does a rename?

# == Schema Information
#
# Table name: users
#
#  id         :integer         not null, primary key
#  email      :string(255)
#  f_name     :string(255)
#  l_name     :string(255)
#  username   :string(255)
#  role_id    :integer
#  picture    :string(255)
#  about_me   :string(255)
#  website    :string(255)
#  created_at :datetime
#  updated_at :datetime
#

---

In the migration file generated by Devise, change the line

  t.string :email,              :null => false, :default => ""

for

  t.change :email, :string,     :null => false, :default => ""

So instead of trying to create a new email colum, the migration changes the existing one to the specifications of Devise.

---

Try rake db:rollback and then try again. When you did it the first time it added the id column. and why are you adding id :integer not null, primary key it's automatic in rails. It should look like this:

class CreateProducts < ActiveRecord::Migration
  def up
    create_table :products do |t|
      t.string :email
      t.text :f_name

      t.timestamps
    end
  end

  def down
    drop_table :products
  end
end

You can get more information here http://guides.rubyonrails.org/migrations.html

---

Resolving this error is simple

1. if you already run the "rake db:migrate" i suggest run rake db:rollback"
2. Go to "timestamp_add_devise_to_whatever.rb and comment out
3. # t.string :email, null: false, default: ""
4. Next also comment this
5. # add_index :users, :email, unique: true
6. Run rake db:migrate and your good to go. :)

---

I hit the same thing adding devise to an existing DB. This fixed it for me:

Modify the autogenerated devise migration:

t.rename :email, :email_old   # move my old email field out of the way 
... 
#add_index :users, :email, :unique => true  ## comment out unique index

Migrate the db.

Make the (new) email field data entries unique interactively w/ a SQL call:

update users set email=id;

Create another migration adding the unique constraint, and run it:

class UniquifyIndex < ActiveRecord::Migration
  def change
        add_index :users, :email, :unique => true
  end