change column to bigint

今天存储数据的时候报错，发现是3435065640超出了常规int的存储长度，

RangeError (3435065640 is out of range for ActiveRecord::Type::Integer with limit 4)

$ bundle exec rails db -p

mysql> desc recommended_videos;
+-------------------------+--------------+------+-----+---------+----------------+
| Field                   | Type         | Null | Key | Default | Extra          |
+-------------------------+--------------+------+-----+---------+----------------+
| id                      | int(11)      | NO   | PRI | NULL    | auto_increment |
| video_id                | varchar(255) | YES  |     |         |                |
| res_desc                | text         | YES  |     | NULL    |                |
| state                   | int(11)      | YES  |     | 0       |                |
| created_at              | datetime     | YES  |     | NULL    |                |           |
+-------------------------+--------------+------+-----+---------+----------------+

　　

http://dev.mysql.com/doc/refman/5.7/en/integer-types.html

12.2.1 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT

MySQL supports the SQL standard integer types INTEGER (or INT) and SMALLINT. As an extension to the standard, MySQL also supports the integer types TINYINT, MEDIUMINT, and BIGINT. The following table shows the required storage and range for each integer type.

Type	Storage	Minimum Value	Maximum Value
	(Bytes)	(Signed/Unsigned)	(Signed/Unsigned)
TINYINT	1	-128	127
		0	255
SMALLINT	2	-32768	32767
		0	65535
MEDIUMINT	3	-8388608	8388607
		0	16777215
INT	4	-2147483648	2147483647
		0	4294967295
BIGINT	8	-9223372036854775808	9223372036854775807
		0	18446744073709551615

 

int的存储上限是2147483647，

所以change_column

class ChangeTotalVvTypeToRecommendedVideos < ActiveRecord::Migration
  def change
    change_column :recommended_videos, :total_vv, :integer, :limit => 8
  end
end

mysql> desc recommended_videos;
+-------------------------+--------------+------+-----+---------+----------------+
| Field                   | Type         | Null | Key | Default | Extra          |
+-------------------------+--------------+------+-----+---------+----------------+
| id                      | int(11)      | NO   | PRI | NULL    | auto_increment |
| state                   | int(11)      | YES  |     | 0       |                |
| sequence                | int(11)      | YES  |     | 1       |                |
| created_at              | datetime     | YES  |     | NULL    |                |
| updated_at              | datetime     | YES  |     | NULL    |                |
| total_vv                | bigint(20)   | YES  |     | NULL    |                |
+-------------------------+--------------+------+-----+---------+----------------+