Rails：如何将add_index添加到现有表 [英] Rails: How to add add_index to existing table

问题描述

我已经迁移了一个名为units的表，其中有几列。我想知道如何使用cmd将独立的add_index迁移到此表中。这段代码是否正确：

I already migrated a table called units with several columns. I was wondering how to migrate in a stand alone 'add_index' to this table using the cmd. Is this code correct:

class AddIndexToUnits < ActiveRecord::Migration
  def self.up
    add_index :units, :lesson_id
  end

  def self.down
    remove :units
  end
end

我感觉self.down可能是错的，我不确定。

I have a feeling the self.down could be wrong, I am unsure.

推荐答案

self.up方法是正确的。用于你的self.down：

The self.up method is correct. Use this for your self.down:

remove_index :units, :column => :lesson_id

这篇关于Rails：如何将add_index添加到现有表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！