PG::UndefinedTable: ERROR: relation "step_images" does not exist

Question

在迁移时我收到以下错误消息：

PG::UndefinedTable: ERROR: relation "step_images" does not exist LINE 5: WHERE a.attrelid = '"step_images"'::regclass ^ : SELECT a.attname, format_type(a.atttypid, a.atttypmod), pg_get_expr(d.adbin, d.adrelid), a.attnotnull, a.atttypid, a.atttypmod FROM pg_attribute a LEFT JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum WHERE a.attrelid = '"step_images"'::regclass AND a.attnum > 0 AND NOT a.attisdropped ORDER BY a.attnum

分贝 class CreateStepImages < ActiveRecord::Migration

  def change
    create_table :step_images do |t|
      t.string :text
      t.attachment :image1
      t.attachment :image2
      t.attachment :image3
      t.attachment :image4
      t.attachment :image5
      t.references :steptation, index: true

      t.timestamps 
    end
  end
end

在 step_image 模型中

class StepImage < ActiveRecord::Base
  belongs_to :steptation
  belongs_to :user
end

步进模式

  has_many :step_images

在 step_images 控制器中

class StepImagesController < ApplicationController
  before_action :find_step_image ,only:[:show,:update,:edit,:destroy]
  before_action :set_steptation, only: [:new, :create]
   def new
    @steptation =Steptation.find(params[:id])
    @step_image = @steptation.step_images.build
    @user = current_user
  end

  def index
  end

  def create
    @step_image = Step_image.new(step_image_params)
    @step_image.user_id = current_user.id
    if @step_image.save
      @steptation.step_images << @step_image 
      redirect_to case_path(id: @steptation.case_id)
    else
      render :new
    end
  end 

  def edit
  end

  def update

    if @step_image.update(step_image_params)
      redirect_to root_path, alert: "steptation Information updated successfully"
    else
      flash.now[:error] = "Couldn't update!"
      render :edit
    end
  end
  def destroy
    @step_image.destroy
    redirect_to root_path, notice: "step_image deleted Successfully"
  end 

private
  def set_steptation
    @steptation = Steptation.find(params[:id])
  end

  def find_step_image
    @step_image = Step_image.find(params[:id])
  end

  def step_image_params
    params.require(:step_image).permit(:text,:image1,:image2,:image3,:image4,:image5)
  end
end

我做到了rake db:rollback STEP=1

$ rake db:rollback STEP=1
  ActiveRecord::SchemaMigration Load (0.9ms)  SELECT "schema_migrations".* FROM "schema_migrations"
  ActiveRecord::SchemaMigration Load (0.3ms)  SELECT "schema_migrations".* FROM "schema_migrations"
Migrating to CreateStepImages (20201119214001)
   (0.1ms)  BEGIN
== 20201119214001 CreateStepImages: reverting =================================
-- drop_table(:step_images)
   (10.3ms)  DROP TABLE "step_images"
   (0.2ms)  ROLLBACK
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:

PG::UndefinedTable: ERROR:  table "step_images" does not exist
: DROP TABLE "step_images"
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `async_exec'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `block in execute'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract_adapter.rb:484:in `block in log'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activesupport-4.2.11.1/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract_adapter.rb:478:in `log'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:154:in `execute'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/schema_statements.rb:127:in `drop_table'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:665:in `block in method_missing'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:634:in `block in say_with_time'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:634:in `say_with_time'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:654:in `method_missing'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:499:in `block in revert'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:498:in `each'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:498:in `revert'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:606:in `exec_migration'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:592:in `block (2 levels) in migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:591:in `block in migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:292:in `with_connection'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:590:in `migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:768:in `migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1023:in `block in execute_migration_in_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1069:in `block in ddl_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `block in transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/transaction.rb:184:in `within_new_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/transactions.rb:220:in `transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1069:in `ddl_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1022:in `execute_migration_in_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:984:in `block in migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:980:in `each'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:980:in `migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:830:in `down'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:935:in `move'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:812:in `rollback'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/railties/databases.rake:118:in `block (2 levels) in <top (required)>'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
/Users/nour/.rvm/gems/ruby-2.5.5/bin/ruby_executable_hooks:24:in `eval'
/Users/nour/.rvm/gems/ruby-2.5.5/bin/ruby_executable_hooks:24:in `<main>'

Caused by:
ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  table "step_images" does not exist
: DROP TABLE "step_images"
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `async_exec'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `block in execute'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract_adapter.rb:484:in `block in log'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activesupport-4.2.11.1/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract_adapter.rb:478:in `log'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:154:in `execute'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/schema_statements.rb:127:in `drop_table'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:665:in `block in method_missing'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:634:in `block in say_with_time'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:634:in `say_with_time'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:654:in `method_missing'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:499:in `block in revert'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:498:in `each'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:498:in `revert'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:606:in `exec_migration'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:592:in `block (2 levels) in migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:591:in `block in migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:292:in `with_connection'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:590:in `migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:768:in `migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1023:in `block in execute_migration_in_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1069:in `block in ddl_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `block in transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/transaction.rb:184:in `within_new_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/transactions.rb:220:in `transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1069:in `ddl_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1022:in `execute_migration_in_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:984:in `block in migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:980:in `each'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:980:in `migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:830:in `down'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:935:in `move'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:812:in `rollback'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/railties/databases.rake:118:in `block (2 levels) in <top (required)>'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
/Users/nour/.rvm/gems/ruby-2.5.5/bin/ruby_executable_hooks:24:in `eval'
/Users/nour/.rvm/gems/ruby-2.5.5/bin/ruby_executable_hooks:24:in `<main>'

Caused by:
PG::UndefinedTable: ERROR:  table "step_images" does not exist
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `async_exec'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `block in execute'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract_adapter.rb:484:in `block in log'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract_adapter.rb:478:in `log'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/database_statements.rb:154:in `execute'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/postgresql/schema_statements.rb:127:in `drop_table'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:665:in `block in method_missing'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:634:in `block in say_with_time'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:634:in `say_with_time'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:654:in `method_missing'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:499:in `block in revert'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:498:in `each'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:498:in `revert'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:606:in `exec_migration'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:592:in `block (2 levels) in migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:591:in `block in migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:292:in `with_connection'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:590:in `migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:768:in `migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1023:in `block in execute_migration_in_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1069:in `block in ddl_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `block in transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/transaction.rb:184:in `within_new_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/transactions.rb:220:in `transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1069:in `ddl_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:1022:in `execute_migration_in_transaction'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:984:in `block in migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:980:in `each'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:980:in `migrate'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:830:in `down'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:935:in `move'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/migration.rb:812:in `rollback'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/activerecord-4.2.11.1/lib/active_record/railties/databases.rake:118:in `block (2 levels) in <top (required)>'
/Users/nour/.rvm/gems/ruby-2.5.5/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
/Users/nour/.rvm/gems/ruby-2.5.5/bin/ruby_executable_hooks:24:in `eval'
/Users/nour/.rvm/gems/ruby-2.5.5/bin/ruby_executable_hooks:24:in `<main>'
Tasks: TOP => db:rollback
(See full trace by running task with --trace)

Answer 1

当运行ning rake db:migrate 时，rails 将在执行迁移之前加载完整的应用程序代码。因此，当你已经定义了StepImageclass时，rails会尝试寻找对应的table。但是，此时 table 尚未创建，从而导致此错误。尝试注释掉 StepImage class 和与之相关的所有内容（例如，通过将文件移出项目文件夹）并重新运行迁移。如果有效，请将文件移回原处。

似乎回滚失败的原因相同：从未创建 step_images table。在这种情况下，我通常会执行以下操作：

将迁移内容放入begin/rescue/end:

默认更改
开始
create_table :step_images 做 |t|
t.string:文本
t.attachment:image1
#...
结束
救援
结束
结束
回滚此迁移以返回原始状态。救援块将捕获错误并且迁移应该成功。
使用 psql 检查 step_images table 是否真的消失了。如果没有，用psql删除。
清理源代码：删除所有与新 step_images table 有关的内容。从这次迁移开始。将其移出项目，这样 rails c 就不会抱怨挂起的迁移。然后将所有模型、控制器等移出项目。删除所有指向新模型的关联（注释掉）。否则，指向不存在的关系 models/tables 将导致更多错误。
清理直到 rails c 成功启动应用程序。
将迁移移回 db/migrations 和运行。
如果成功，请将所有内容重新带回。如果不确定，请分多个小步骤进行，并在中间通过运行ning rails c.
检查

希望对您有所帮助！

PG::UndefinedTable: ERROR: relation "step_images" does not exist

PG::UndefinedTable: ERROR: relation "step_images" does not exist

migration

postgresql

ruby-on-rails

database-migration

rails-migrations