Rails&Postgres:迁移到change_colomn会出现错误"无法转换为没有时区的类型时间戳"

Question

用于将"deleted_at"时间列转换为日期时间列的Rails迁移失败.关于如何解决这个问题的任何想法？如果相关的话,这是Postgres的全新安装.

-- change_column(:products, :deleted_at, :datetime)


 PGError: ERROR:  column "deleted_at" cannot be cast to type timestamp without time zone
: ALTER TABLE "products" ALTER COLUMN "deleted_at" TYPE timestamp

Answer 1

在Rails中,这看起来像

class ChangeStatusUpdatedAtToDateTime < ActiveRecord::Migration
  def up
    remove_column :bookings, :status_updated_at
    add_column :bookings, :status_updated_at, :datetime
  end

  def down
    remove_column :bookings, :status_updated_at
    add_column :bookings, :status_updated_at, :time
  end
end

Answer 2

您不能在时间戳("datetime")之间更改字段的类型,因为无法转换值 - 数据库不知道日期.

但是,您可以删除并重新创建列:

ALTER TABLE products DROP COLUMN deleted_at;
ALTER TABLE products ADD COLUMN deleted_at timestamp;

或者,如果此字段设置为NOT NULL,则应该执行以下操作:

ALTER TABLE products ADD COLUMN deleted_at timestamp NOT NULL;

但是如果你像Sean一样坚持在这个表中保留假值,你可以使用ALTER ... TYPE ...使用像这样:

ALTER TABLE products ALTER COLUMN deleted_at TYPE timestamp USING
    CASE WHEN deleted_at IS NOT NULL THEN timestamp '1970-01-01 00:00:00' END;
-- Or:
ALTER TABLE products ALTER COLUMN deleted_at
    TYPE timestamp USING date '1970-01-01' + deleted_at;