rails 3.2迁移无法在change方法中为create_table添加索引

Question

这是我在rails 3.2.2中的迁移:

class CreateStatistics < ActiveRecord::Migration
  def change
    create_table :statistics do |t|
      t.string :name
      t.integer :item_id
      t.integer :value
      t.text :desc

      t.timestamps
      t.index [:name, :item_id]
    end

  end
end

这是迁移错误:

==  CreateStatistics: migrating ===============================================
-- create_table(:statistics)
ActiveRecord::ConnectionAdapters::TableDefinition
rake aborted!
An error has occurred, all later migrations canceled:

undefined method `index' for #<ActiveRecord::ConnectionAdapters::TableDefinition:0xbd16888>

Tasks: TOP => db:migrate
(See full trace by running task with --trace)

什么是创建索引的正确方法？

Answer 1

您仍然可以将索引添加为"更改"迁移的一部分.您只需要在以下呼叫之外执行此操作create_table:

class CreateStatistics < ActiveRecord::Migration
  def change
    create_table :statistics do |t|
      t.string :name
      t.integer :item_id
      t.integer :value
      t.text :desc

      t.timestamps
    end

    add_index :statistics, [:name, :item_id]
  end
end

这会正确地创建表,然后在"向上"迁移时创建索引并删除索引,然后在"向下"迁移时删除表.