不能耙分贝：迁移

我遇到了One Month Rails应用程序的问题。不能耙分贝：迁移

我已经运行

rails generate migration add_user_id_to_pins user_id:integer:index

但是，当我尝试直接运行

rake db:migrate

后，我产生的迁移，我得到这个错误：

== 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'

这些都是我在迁移中产生的文件的内容：

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

我认为这可能是因为我有多次尝试生成迁移，但我删除了以前的迁移，所以我不确定是什么导致了这种情况。

来源

2014-03-19 user3172050

您试图在数据库中两次添加user_id列。 user_id列创建引脚表时添加到pins表。注意，迁移上线失败（如果你试图USER_ID再次添加到销表）

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

迁移文件应该是这样：

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

来源

2014-03-19 17:22:49

感谢您的回答。我认为你解决了我的问题，但它不幸造成了另一个问题。现在我收到错误：“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） “当尝试db：migrate时。 – user3172050

首先，您需要'rake db：rollback version = version_number'，其中'20140125191228'替换version_number，如果迁移文件是'20140125191228_create_pins.rb' –

运行后'rake db：migrate'。 –

不能耙分贝：迁移

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