rails-migrations

ruby-添加和删除参考的Rails迁移 ¶

使用rails generate migration AddClientToUser创建迁移文件后，我可以像这样编辑迁移文件：

class AddClientToUser < ActiveRecord::Migration
  def self.up
    change_table :users do |t|
      t.references :client
    end
  end

  def self.down
    change_table :users do |t|
      t.remove :client_id
    end
  end
end

这是反转迁移中添加的参考列的正确方法吗？

ruby ruby-on-rails-3 rails-migrations

trans by 2020-08-12T09:15:54Z

Rails 4：通过迁移从表列中删除非null约束吗？¶

鉴于以下name：

  create_table "people", force: true do |t|
    t.string   "name",  null: false
    t.integer  "age"
    t.integer  "height"
    t.string   "email"
    t.boolean  "married",  default: false
    t.text     "bio"
    t.integer  "fav_number"
    t.decimal  "lucky_num",  precision: 2, scale: 2
    t.datetime "birthday"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

我想删除name的默认值null: false。我尝试使用change_column_default运行单独的迁移，但是这对schema.rb没有影响。有什么建议吗？

rails-migrations ruby-on-rails-4

trans by 2020-08-09T07:09:05Z

ruby-如何在Rails迁移中检查数据库类型？¶

我进行了以下迁移，并且希望能够检查与环境相关的当前数据库是否为mysql数据库。如果是mysql，则要执行特定于数据库的SQL。

我该怎么办？

class AddUsersFb < ActiveRecord::Migration

  def self.up
    add_column :users, :fb_user_id, :integer
    add_column :users, :email_hash, :string
    #if mysql
    #execute("alter table users modify fb_user_id bigint")
  end

  def self.down
    remove_column :users, :fb_user_id
    remove_column :users, :email_hash
  end

end

ruby-on-rails ruby migration rails-migrations

trans by 2020-08-07T09:49:16Z

ruby on rails-Gem :: LoadError：无法激活pg（〜> 0.18），已经激活了pg-1.0.0 ¶

这个问题已经在这里有了答案：

使用Postgres适配器的Rails应用程序无法激活pg 1个答案

我一直在做此处找到的Rails教程，并且成功完成了必须使用$ rails db：migrate迁移Comments迁移的过程。在此之前，我已经能够生成Article模型并进行迁移，从而可以毫无问题地进行迁移。在这两次迁移之间，我的Gemfile中没有任何变化，因此我不确定Bundler遇到了什么问题。

这是错误，然后是完整的命令行输出，以及我的Gemfile和schema.rb：

Gem::LoadError: can't activate pg (~> 0.18), already activated pg-1.0.0.

Gem::LoadError: Specified 'postgresql' for database adapter, but the gem is not loaded. Add `gem 'pg'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).

完整的命令行输出

xxx:gangelo: ~/dev/rails/test/blog (master*) ☠  rbenv exec rails db:migrate
rails aborted!
Gem::LoadError: Specified 'postgresql' for database adapter, but the gem is not loaded. Add `gem 'pg'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:188:in `rescue in spec'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:185:in `spec'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:880:in `establish_connection'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:58:in `establish_connection'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:124:in `block (2 levels) in <class:Railtie>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `instance_eval'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `block in execute_hook'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:60:in `with_execution_control'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:65:in `execute_hook'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `each'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:326:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:25:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:6:in `<class:MySQLDatabaseTasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:3:in `<module:Tasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:2:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:1:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:74:in `<module:DatabaseTasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:35:in `<module:Tasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:2:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:1:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:34:in `block (3 levels) in <class:Railtie>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:21:in `block in perform'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:18:in `perform'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/command.rb:46:in `invoke'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands.rb:16:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/bin/rails:9:in `require'
/Users/gangelo/dev/rails/test/blog/bin/rails:9:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `load'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `call'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client.rb:30:in `run'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/bin/spring:49:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'

Caused by:
Gem::LoadError: can't activate pg (~> 0.18), already activated pg-1.0.0. Make sure all dependencies are added to Gemfile.
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/postgresql_adapter.rb:2:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:186:in `spec'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:880:in `establish_connection'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:58:in `establish_connection'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:124:in `block (2 levels) in <class:Railtie>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `instance_eval'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `block in execute_hook'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:60:in `with_execution_control'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:65:in `execute_hook'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `each'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:326:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/base.rb:25:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:6:in `<class:MySQLDatabaseTasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:3:in `<module:Tasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:2:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:1:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:74:in `<module:DatabaseTasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:35:in `<module:Tasks>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:2:in `<module:ActiveRecord>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:1:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/activerecord-5.1.4/lib/active_record/railtie.rb:34:in `block (3 levels) in <class:Railtie>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:21:in `block in perform'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:18:in `perform'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/command.rb:46:in `invoke'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/railties-5.1.4/lib/rails/commands.rb:16:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/bin/rails:9:in `require'
/Users/gangelo/dev/rails/test/blog/bin/rails:9:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `load'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `call'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/client.rb:30:in `run'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/bin/spring:49:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load'
/Users/gangelo/dev/rails/test/blog/vendor/bundle/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `<top (required)>'
/Users/gangelo/dev/rails/test/blog/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'
Tasks: TOP => db:migrate => db:load_config
(See full trace by running task with --trace)

宝石文件

source 'https://rubygems.org'

ruby '2.3.1'

git_source(:github) do |repo_name|
  repo_name = "#{repo_name}/#{repo_name}" unless repo_name.include?("/")
  "https://github.com/#{repo_name}.git"
end


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.1.4'

# Use sqlite3 as the database for Active Record
# gem 'sqlite3'

# Use postgres as the database for Active Record
gem 'pg'

# Use Puma as the app server
gem 'puma', '~> 3.7'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 3.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '~> 2.13'
  gem 'selenium-webdriver'
end

# gma - start
group :development, :test do
  gem 'rspec-rails', '~> 3.5', '>= 3.5.2'
  gem 'rspec-activemodel-mocks', '~> 1.0', '>= 1.0.3'
  gem 'shoulda-matchers', '~> 3.1', '>= 3.1.1'
  gem 'factory_bot_rails', '~> 4.8', '>= 4.8.2'
  gem 'ffaker', '~> 2.2'
  # gem 'timecop', '~> 0.8.1'
end
# gma - end

group :development do
  # Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
  gem 'web-console', '>= 3.3.0'
  gem 'listen', '>= 3.0.5', '< 3.2'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

模式.rb

ActiveRecord::Schema.define(version: 20180110153949) do
  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"

  create_table "articles", force: :cascade do |t|
    t.string "title"
    t.text "text"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end
end

迁移档案

class CreateComments < ActiveRecord::Migration[5.1]
  def change
    create_table :comments do |t|
      t.string :commenter
      t.text :body
      t.references :article, foreign_key: true

      t.timestamps
    end
  end
end

ruby-on-rails postgresql ruby rails-migrations bundler

trans by 2020-07-22T09:00:08Z

ruby on rails-如何使remove_column可逆？¶

我有一个删除列的迁移：

def change
  remove_column :foos, :bar, :boolean
end

当我尝试进行up的迁移时，出现以下错误：

remove_column is only reversible if given a type.

ActiveRecord :: Migration文档说以下是up的签名：

remove_column(table_name, column_name, type, options)

因此，在这种情况下，我的类型应该是up，我希望迁移是可逆的。我想念什么？

我当然可以将其分解为up和down迁移以避免此问题，但是我想了解为什么change语法在这种情况下不起作用。

ruby-on-rails rails-migrations

trans by 2020-07-13T00:06:00Z

ruby-在Rails迁移中，如何删除字段的限制 ¶

以下正确吗？

 change_column :tablename, :fieldname, :limit => null

ruby-on-rails ruby rails-migrations

trans by 2020-02-16T02:39:17Z

将通过Rails迁移删除列，删除与该列关联的索引 ¶

在Rails 2中，通过Rails迁移删除列还会更改/删除与该列关联的索引吗？如果不是，您还必须手动更改/删除每个索引，它是否应该自动化？

谢谢（来自Rails新手）

ruby-on-rails rails-migrations

trans by 2020-02-13T03:37:25Z

Ruby on rails-运行rake：db migration命令时，出现错误“未初始化的常量CreateArticles”¶

我创建了一个模型红宝石脚本/生成模型文章（简单的内容）

这是迁移文件create_articles.rb：

def self.up
  create_table :articles do |t|
    t.column :user_id, :integer
    t.column :title, :string
    t.column :synopsis, :text, :limit => 1000
    t.column :body, :text, :limit => 20000
    t.column :published, :boolean, :default => false
    t.column :created_at, :datetime
    t.column :updated_at, :datetime
    t.column :published_at, :datetime
    t.column :category_id, :integer
  end

def self.down
  drop_table :articles
 end
end

当我运行rake：db migration命令时，我收到一个错误的rake中止了！ “未初始化的常量CreateArticles。”

有谁知道为什么这个错误不断发生？

ruby-on-rails rails-migrations rake

trans by 2020-02-08T20:23:38Z

连接选项卡的Rails命名约定 ¶

这个问题源于：在创建rails join table之后如何链接表单

我正在创建我的产品模型和类别模型之间的联接表。

联接表应命名为什么？ Categories_products或category_products还是其他？

ruby-on-rails ruby-on-rails-3 rails-migrations ruby-on-rails-3.1

trans by 2020-01-29T09:57:07Z

heroku-在Rails 3中删除表和删除模型的最佳方法是什么？¶

我有一个不再需要在我的App中使用的模型和表格，我可以将它们放在此处，但我想删除它们以保持整洁。

我正在尝试找出删除它们的最佳方法，而不会弄乱我的迁移文件和db / schema.rb文件及其对我的生产环境可能产生的任何副作用，我的应用程序在Heroku上。我在本地计算机和heroku上都使用PostgreSQL。

到目前为止，我已经找到了两种方法来执行此操作，但不确定哪种方法是最佳方法。

方法一

我考虑过只进入数据库并删除表，然后销毁模型。

rails db
DROP TABLE table_name
\q
rails destroy model model_name

如果执行此操作，此模型/表的迁移将发生什么？我对此模型进行了两次迁移，分别是timestamp_create_modelname和add_attribute_to_table名称。

此方法还会更新db / schema.rb文件吗？

当我将应用程序推送到Heroku时，我怀疑模型会被删除，但表格会保留在原位，是否有heroku命令可以放下表格。

方法二

我读过的另一种方法是生成一个新的迁移，以删除表然后销毁模型。

rails generate migration drop_tablename

＆然后更新以下文件：

db / migrate / timestamp drop_table名称（已更新，以回应下面的Dan回答）

class DropTablename < ActiveRecord::Migration
  def up
    drop_table :tablename
  end

  def down
    create_table :tablename do |t|
      t.string :table_column
      t.references :anothertable

      t.timestamps        
    end
    add_index :tablenames, :anothertable_id
  end
end

＆然后在终端中：

rake db:migrate
rails destroy model model_name
rake db:migrate
git add .
git commit -m "removed table/model_name"
git push heroku master
heroku run rake db:migrate
heroku restart

这似乎是最好的方法，但是较旧的迁移文件会怎样？每次我运行rake db：migrate时，它们是否仍会保留并更新db / shema，仅被db / migrate / timestamp_drop_tablename覆盖？

我很乐于尝试第二种方法，但是希望有经验的人参与其中，并告诉我这样做的方法。

heroku ruby-on-rails-3 rails-migrations rails-models

trans by 2020-01-15T11:52:29Z

Rails迁移：表的add_reference但外键的列名与Rails约定不同 ¶

我有以下两个模型：

class Store < ActiveRecord::Base
    belongs_to :person
end

class Person < ActiveRecord::Base
    has_one :store
end

这是问题所在：我正在尝试创建一个迁移，以在人员表中创建外键。但是，引用Store外键的列并未像rails约定那样被命名为store_id，而是被命名为foo_bar_store_id。

如果我遵循Rails约定，我将进行如下迁移：

class AddReferencesToPeople < ActiveRecord::Migration
  def change
    add_reference :people, :store, index: true
  end
end

但是，这将不起作用，因为列名不是store_id，而是foo_bar_store_id。因此，如何指定外键名称只是不同，但仍保持index：true以保持快速性能？

ruby-on-rails rails-migrations

trans by 2020-01-09T01:32:44Z

我为什么要运行'rake db：migrate RAILS_ENV = test'？¶

在运行迁移后，在Rails 4.0.0.rc1，Ruby 2.0.0上，尝试通过rake db:migrate RAILS_ENV=test运行测试时，看到以下错误：

/Users/peeja/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/activerecord-4.0.0.rc1/lib/active_record/migration.rb:376:in `check_pending！'：迁移正在等待；运行'rake db：migrate RAILS_ENV = test'解决此问题。（ActiveRecord :: PendingMigrationError）

那似乎不对。没有人迁移他们的测试数据库，对吗？他们是rake db:migrate RAILS_ENV=test，说实话，我已经忘记了。因此，我运行rake db:test:prepare并再次运行rspec命令……并看到相同的错误。

如果我实际上是rake db:migrate RAILS_ENV=test，该错误实际上会消失。

这是怎么回事？这是Rails 4中的新功能吗？

ruby-on-rails rails-migrations ruby-on-rails-4

trans by 2019-11-08T10:37:20Z

rails中的t.belongs_to和t.references有什么区别？¶

t.references和t.belongs_to之间的差异有什么不同？为什么我们有这两个不同的词？在我看来他们做同样的事情？试过一些谷歌搜索，但没有找到解释。

class CreateFoos < ActiveRecord::Migration
  def change
    create_table :foos do |t|
      t.references :bar
      t.belongs_to :baz
      # The two above seems to give similar results
      t.belongs_to :fooable, :polymorphic => true
      # I have not tried polymorphic with t.references
      t.timestamps
    end
  end
end

ruby-on-rails-3 rails-migrations ruby-on-rails-3.1

trans by 2019-07-24T19:25:56Z

ruby on rails - 如何生成迁移以使引用具有多态性 ¶

我有一个Products表，想要添加一列：

t.references :imageable, :polymorphic => true

我试图通过以下方式为此生成迁移：

$ rails generate migration AddImageableToProducts imageable:references:polymorphic

但我显然做错了。任何人都可以提出任何建议吗？谢谢

当我在生成迁移后尝试手动将其放入时，我这样做：

class AddImageableToProducts < ActiveRecord::Migration
  def self.up
    add_column :products, :imageable, :references, :polymorphic => true
  end

  def self.down
    remove_column :products, :imageable
  end
end

它仍然没有奏效

ruby-on-rails rails-migrations polymorphic-associations

trans by 2019-07-10T10:41:46Z

ruby on rails - 在“引用”迁移中指定列名 ¶

我想在Rails中制作user_id，引用另一个表。通常，我会这样做：

add_column :post, :user, :references

这将在posts表中创建名为user_id的列。但是，如果，而不是user_id，我想要像author_id？我怎样才能做到这一点？

ruby-on-rails ruby-on-rails-3 rails-migrations activerecord

trans by 2019-07-09T07:24:14Z

ruby on rails - ActiveRecord数据类型的文档页面在哪里？¶

我找不到包含所有数据类型列表的活动记录文档页面。

有人可以帮我吗？

ruby-on-rails rails-migrations

trans by 2019-06-03T10:52:37Z

在rails中显示待定迁移 ¶

是否有rake任务显示rails应用程序中的挂起迁移？

javascript ruby-on-rails c# reactjs node.js c redis rails-migrations

trans by 2019-05-12T03:22:03Z

ruby on rails - 将时间戳添加到现有选项卡 ¶

我需要将时间戳（created_at updated_at）添加到现有表。我尝试了以下代码，但它没有用。我也尝试过我在网上找到的其他解决方案，但它们也不起作用。

class AddTimestampsToUser < ActiveRecord::Migration
    def change_table
      add_timestamps(:users)
    end
end

我该怎么做？

java javascript ruby-on-rails reactjs html5 node.js css3 elasticsearch ruby rails-migrations rails-activerecord

trans by 2019-04-26T18:42:34Z

mysql - 回滚失败的Rails迁移 ¶

如何回滚失败的rails迁移？我希望rake db:rollback可以撤消失败的迁移，但不会，它会回滚先前的迁移（失败的迁移减去1）。并且rake db:migrate:down VERSION=myfailedmigration也不起作用。我已经碰到了几次，这非常令人沮丧。这是我为复制问题所做的简单测试：

class SimpleTest < ActiveRecord::Migration
  def self.up
    add_column :assets, :test, :integer
    # the following syntax error will cause the migration to fail
    add_column :asset, :test2, :integer
  end

  def self.down
    remove_column :assets, :test
    remove_column :assets, :test2
  end
end

结果：

==  SimpleTest: migrating =====================================================
-- add_column(:assets, :test, :integer)
   -> 0.0932s
-- add_column(:asset, :error)
rake aborted!
An error has occurred, all later migrations canceled:

wrong number of arguments (2 for 3)

好吧，让我们回滚：

$ rake db:rollback
==  AddLevelsToRoles: reverting ===============================================
-- remove_column(:roles, :level)
   -> 0.0778s
==  AddLevelsToRoles: reverted (0.0779s) ======================================

是吧？这是我在SimpleTest之前的最后一次迁移，而不是失败的迁移。（哦，如果迁移输出包含版本号，那将会很好。）

因此，让我们尝试运行失败的迁移SimpleTest：

$ rake db:migrate:down VERSION=20090326173033
$

没有任何事情发生，也没有输出。但也许它还是进行了迁移？因此，我们修复SimpleTest迁移中的语法错误，并尝试再次运行它。

$ rake db:migrate:up VERSION=20090326173033
==  SimpleTest: migrating =====================================================
-- add_column(:assets, :test, :integer)
rake aborted!
Mysql::Error: Duplicate column name 'test': ALTER TABLE `assets` ADD `test` int(11)

不。显然迁移：down不起作用。它并没有失败，它只是没有执行。

除了手动进入数据库并删除它，然后运行测试之外，没有办法摆脱那个重复的表。必须有一个比这更好的方法。

ruby-on-rails mysql rails-migrations rails-activerecord

trans by 2019-04-21T10:07:39Z

Rails迁移：撤消列的默认设置 ¶

我有问题，我在Rails中有一个迁移设置列的默认设置，如下例所示：

def self.up
  add_column :column_name, :bought_at, :datetime, :default => Time.now
end

假设，我想在以后的迁移中删除默认设置，如何使用rails迁移？

我目前的解决方法是在rails迁移中执行自定义sql命令，如下所示：

def self.up
  execute 'alter table column_name alter bought_at drop default'
end

但我不喜欢这种方法，因为我现在依赖于底层数据库如何解释这个命令。如果数据库发生更改，此查询可能不再起作用，迁移将被破坏。那么，有没有办法表示在rails中删除列的默认设置？

ruby-on-rails rails-migrations

trans by 2019-03-20T11:29:41Z

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