不能耙分貝：遷移

我遇到了One Month Rails應用程序的問題。不能耙分貝：遷移

我已經運行

rails generate migration add_user_id_to_pins user_id:integer:index

但是，當我嘗試直接運行

rake db:migrate

後，我產生的遷移，我得到這個錯誤：

== AddUserIdToPins: migrating ================================================ 
-- add_column(:pins, :user_id, :integer) 
rake aborted! 
An error has occurred, this and all later migrations canceled: 

SQLite3::SQLException: duplicate column name: user_id: ALTER TABLE "pins" ADD "user_id"  integer/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/sqlite3- 1.3.9/lib/sqlite3/database.rb:91:in `initialize' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/sqlite3-1.3.9/lib/sqlite3/database.rb:91:in  `new' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/sqlite3-1.3.9/lib/sqlite3/database.rb:91:in `prepare' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/sqlite3-1.3.9/lib/sqlite3/database.rb:134:in `execute' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/activerecord-4.0.3/lib/active_record/connection_adapters/sqlite3_adapter.rb:331:in `block in execute' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/activerecord-4.0.3/lib/active_record/connection_adapters/abstract_adapter.rb:435:in `block in log' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/activesupport-4.0.3/lib/active_support/notifications/instrumenter.rb:20:in `instrument' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/activerecord-4.0.3/lib/active_record/connection_adapters/abstract_adapter.rb:430:in `log' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/activerecord-4.0.3/lib/active_record/connection_adapters/sqlite3_adapter.rb:331:in `execute' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/activerecord-4.0.3/lib/active_record/connection_adapters/abstract/schema_statements.rb:360:in `add_column' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/activerecord-4.0.3/lib/active_record/connection_adapters/sqlite3_adapter.rb:454:in `add_column' 
/home/colin/.rvm/gems/ruby-2.0.0-p451/gems/activerecord-4.0.3/lib/active_record/migration.rb:625:in `block in method_missing'

這些都是我在遷移中產生的文件的內容：

class AddUserIdToPins < ActiveRecord::Migration 
    def change 
    create_table :pins do |t| 
     t.integer :user_id 
     t.timestamps 
    end 
    add_index :pins, :user_id 
    end 
    def change 
     Pins.reset_column_information  
    add_column :pins, :user_id, :integer 
    add_index :pins, :user_id 
    end 
end

我認爲這可能是因爲我有多次嘗試生成遷移，但我刪除了以前的遷移，所以我不確定是什麼導致了這種情況。

來源

2014-03-19 user3172050

您試圖在數據庫中兩次添加user_id列。 user_id列創建引腳表時添加到pins表。注意，遷移上線失敗（如果你試圖USER_ID再次添加到銷表）

add_column(:pins, :user_id, :integer) rake aborted!

def change 
    create_table :pins do |t| 
     t.integer :user_id ## Added first time 
     t.timestamps 
    end 
    add_index :pins, :user_id 
end 
def change 
    Pins.reset_column_information  
    add_column :pins, :user_id, :integer ## Adding second time : Here you get the error 
    add_index :pins, :user_id 
end

遷移文件應該是這樣：

class AddUserIdToPins < ActiveRecord::Migration 
    def change 
    create_table :pins do |t| 
     t.integer :user_id 
     t.timestamps 
    end 
    add_index :pins, :user_id 
    Pin.reset_column_information ## Model name should be singular 
    end 
end

來源

2014-03-19 17:22:49

感謝您的回答。我認爲你解決了我的問題，但它不幸造成了另一個問題。現在我收到錯誤：「SQLite3 :: SQLException：table」pins「已存在：CREATE TABLE」pins「（」id「INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL，」user_id「integer，」created_at「datetime，」updated_at「datetime）「當嘗試db：migrate時。 – user3172050

首先，您需要'rake db：rollback version = version_number'，其中'20140125191228'替換version_number，如果遷移文件是'20140125191228_create_pins.rb' –

運行後'rake db：migrate'。 –

不能耙分貝：遷移

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