如何在ActiveRecord的迁移重置自动增量字段？ [英] How to reset auto increment field in a ActiveRecord migration?

问题描述

在我的移民，我有：

def up
   MyModel.destroy_all
   MyModel.create!({:id=>1,:name=>'foo'})
   MyModel.create!({:id=>2,:name=>'fooBar'})
   MyModel.create!({:id=>3,:name=>'fooNull'})
end

因为我需要重写，这是已经在my_models表中的数据。

because I need to override data that was already on my_models table

不过，即使我指定了 ID 关于MySQL继续编号从位置就已经是。

But Even though I'm specifying the id on MySQL it continues the numbering from the position it already was.

我需要休息的自动递增的计数器 ID 来只有这3个新的与我的Ruby on Rails应用的ID值槽活动记录迁移记录。

I need to rest the counter on the auto increment for id to have only this 3 new records with that id values trough Active Record migration on my Ruby on Rails application.

推荐答案

您有两个不同的问题。其中之一是，您要指定与质量分配的ID，导轨不会允许你这样做。查看创建的ActiveRecord 一种方式来做到这一点重写ID。

You have 2 separate issues. One is that you are trying to specify the id with mass assignment, rails won't allow you to do that. See Overriding id on create in ActiveRecord for a way to do that.

另一个问题是，自动递增不复位。每个DBMS都有设置一个增量计数器的一种独特的方式，和轨道不给你访问他们一个通用的方式，但它是为一些人（而不是MySQL的）实现的，看到的导轨的方式来重设上id字段的种子

The other issue is that the auto-increment isn't resetting. Each DBMS has a unique way of setting an increment counter, and rails doesn't give you a generic way to access them, although it is implemented for some of them (not MySQL), see Rails way to reset seed on id field

所以你需要运行这个MySQL的特定的SQL，这是一样的东西：

So you'll need to run the MySQL specific SQL for this, which is something like:

ALTER TABLE my_models AUTO_INCREMENT = 1;

这应该重置的数量在表中最大的ID后（1如果没有任何）

This should reset to the number after the largest id in your table (1 if there aren't any)

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