Rails 的 change_column 迁移问题

Question

我将 PostGres 和 Rails 6 用于 Docker 项目。我有以下迁移文件，用于将列类型从字符串或数字转换为整数：

class ChangeColumnTypes < ActiveRecord::Migration[6.0]
  def change
    change_column :drivers, :yearOfBirth, :integer, using: 'yearOfBirth::integer'
    change_column :drivers, :racingNumber, :integer, using: 'racingNumber::integer'
    change_column :drivers, :noRaces, :integer, using: 'noRaces::integer'
    change_column :drivers, :noPoles, :integer, using: 'noPoles::integer'
    change_column :drivers, :noPodiums, :integer, using: 'noPodiums::integer'
    change_column :drivers, :noWins, :integer, using: 'noWins::integer'
    change_column :drivers, :user_id, :integer, using: 'user_id::integer'
  end
end

当我运行迁移时，我会收到类似的错误

Caused by:
myapp_1     | PG::UndefinedColumn: ERROR:  column drivers.yearofbirth does not exist
myapp_1     | LINE 1: ...rivers" ALTER COLUMN "drivers" TYPE integer USING drivers.ye...

HINT:  Perhaps you meant to reference the column "drivers.yearOfBirth".

我的专栏是驼峰式的，这可能是问题，因为 yearOfBirth 名称是正确的。有没有办法解决？谢谢

Answer 1

你可以试试

change_column :drivers, :yearOfBirth, 'integer USING CAST(yearOfBirth AS integer)'

如果这不起作用（为了安全起见，我会在尝试之前将其全部备份）：

1. 使用另一个名称创建一个新的 int 列
2. 将转换后的数据移到那里
3. 删除原始列
4. 将新列名称更改为原始名称

create_column :drivers, :yearOfBirthInt, :integer

Driver.update_all('yearOfBirthInt = CAST(yearOfBirth AS integer)')

# If the above doesn't work, try this, but it's a lot slower:
# Driver.transaction do
#   Driver.each { |d| d.update!(yearOfBirthInt: d.yearOfBirth.to_i) }
# end

remove_column :drivers, :yearOfBirth
rename_column :drivers, :yearOfBirthInt, :yearOfBirth