message_all表中添加type索引

db/migrate/20160321071740_add_index_to_message_alls.rb

@@ -1,5 +1,5 @@
 class AddIndexToMessageAlls < ActiveRecord::Migration
   def change
-    add_index :message_alls, [:user_id, :message_id, :message_type, :created_at]
+    add_index :message_alls, [:user_id, :message_id, :created_at]
   end
 end

db/migrate/20160321085313_add_index_mtye_to_message_alls.rb

@@ -0,0 +1,5 @@
+class AddIndexMtyeToMessageAlls < ActiveRecord::Migration
+  def change
+    add_index :message_alls, [:message_type]
+  end
+end