check index exist

add_index 之前檢查一下
<br />class AddMissingIndexes < ActiveRecord::Migration<br /> def self.up<br /> check_add_index :groups, :id<br /> check_add_index :about_states, :confirm_email_code<br /> check_add_index :messages, :id<br /> end<br /><br /> def self.down<br /> check_remove_index :groups, :id<br /> check_remove_index :about_states, :confirm_email_code<br /> check_remove_index :messages, :id<br /> end<br /><br /> def self.check_add_index(table, column)<br /> add_index table, column unless check_index_exist(table, column)<br /> end<br /><br /> def self.check_remove_index(table, column)<br /> remove_index table, column if check_index_exist(table, column)<br /> end<br /><br /> # indexes 可以找出talbe 的 indexes<br /> # index_name 可以產生該生成的 index name<br /> def self.check_index_exist(table, columns)<br /> ActiveRecord::Base.connection.indexes(table).map(&:name).include?(ActiveRecord::Base.connection.index_name(table, columns))<br /> end<br /><br />end<br />