Question

在删除我的专栏“type”

之后，我在我的heroku应用上迁移数据库时遇到问题

class RemoveTypeFromMandats < ActiveRecord::Migration[5.0]
def change
remove_column :mandats, :type, :boolean
end
end

我放弃了这个专栏，因为我的名字错了，列不能命名为“type”

但是现在当我尝试在heroku上迁移我的数据库时出现此错误

D, [2017-03-13T08:39:10.619658 #4] DEBUG -- :    (3.9ms)  ALTER TABLE      "mandats" DROP "type"
D, [2017-03-13T08:39:10.623526 #4] DEBUG -- :    (3.5ms)  ROLLBACK
D, [2017-03-13T08:39:10.627178 #4] DEBUG -- :    (3.3ms)  SELECT   pg_advisory_unlock(157042690317842070)
rails aborted!
StandardError: An error has occurred, this and all later migrations  canceled:

PG::UndefinedColumn: ERROR:  column "type" of relation "mandats" does not exist
: ALTER TABLE "mandats" DROP "type"

Answer 1

您可以尝试column_exists?

class RemoveTypeFromMandats < ActiveRecord::Migration[5.0]
  def change
    if column_exists? :mandats, :type         
      remove_column :mandats, :type, :boolean
    end
  end
end

列删除后，rails DB heroku迁移错误

1 个答案: