pg：：undefinedtable：error：表“table-name”不存在

Question

我在搞乱我的数据库，创建和删除表。在将迁移文件推送到Heroku后，我删除了几个迁移文件。之前，我创建了一个表'moms'。后来我想重命名它，所以我删除了'moms'并创建了新表'minutes_of_meetings'。我做了$rake db:migrate，一切都成功完成了，我的应用程序在localhost上运行得很好。

在将其推送到heroku之后，当我执行$heroku运行rake db：migrate时，它生成了以下日志：

  ActiveRecord::SchemaMigration Load (0.7ms)  SELECT "schema_migrations".* FROM "schema_migrations"
  Migrating to DropMoms (20150823142852)
  (0.6ms)  BEGIN
             == 20150823142852 DropMoms: migrating =========================================
                 -- drop_table(:moms)
             (0.9ms)  DROP TABLE "moms"
             PG::UndefinedTable: ERROR:  table "moms" does not exist
             : DROP TABLE "moms"
             (0.5ms)  ROLLBACK
             rake aborted!
             StandardError: An error has occurred, this and all later migrations canceled:

                                                                                     PG::UndefinedTable: ERROR:  table "moms" does not exist
             : DROP TABLE "moms"/app/vendor/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `async_exec'
      /app/vendor/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `block in execute'

我在heroku中创建了一个新表'moms'，以便在迁移运行时删除它。我是这么做的：

$ heroku run Ruby console for rails-app-name >> ActiveRecord::Migration.create_table :moms 

class CreateMoms < ActiveRecord::Migration
  def change
    create_table :moms do |t|
      t.string :name
      t.timestamp null: false
    end
  end
end

Running `rake db:migrate:up` attached to terminal... up, run.1729
rake aborted!
VERSION is required
/app/vendor/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/railties/databases.rake:78:in `block (3 levels) in <top (required)>'
Tasks: TOP => db:migrate:up
(See full trace by running task with --trace)
WARNING: Toolbelt v3.41.3 update available.

在heroku上运行rake db：migrate：down

Running `rake db:migrate:down` attached to terminal... up, run.6389
rake aborted!
VERSION is required - To go down one migration, run db:rollback
/app/vendor/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/railties/databases.rake:86:in `block (3 levels) in <top (required)>'
Tasks: TOP => db:migrate:down
(See full trace by running task with --trace)
WARNING: Toolbelt v3.41.3 update available.

Answer 1

rake db:schema:load将从heroku数据库中删除所有数据。请确保在Heroku上有数据备份。如果您还没有heroku数据库的备份，您可以通过使用heroku PGBackups轻松地做到这一点

似乎您的架构搞乱了。只需使用rake db:schema:load将架构加载到数据库，然后再次运行迁移：

heroku run rake db:schema:load
heroku run rake db:migrate