开发者

Ruby on Rails: Instantiate associated models with find_by_sql?

开发者 https://www.devze.com 2022-12-22 11:58 出处:网络
Apparently, include and select can\'t be used simultaneously on a Rails find query, and this has been repeatedly marked as wontfix:

Apparently, include and select can't be used simultaneously on a Rails find query, and this has been repeatedly marked as wontfix:

http://dev.rubyonrails.org/ticket/7147

http://dev.rubyonrails.org/ticket/5371

This strikes me as very inconvenient, because the times I'd want to use include are exactly the same times I'd want to use select - when every bit of performance counts.

Is there any way to work around this and manually generate a combined include-with-select using find_by_sql, or any other method? The trouble is, I'm not aware of any way to emulate the functionality of include, where it instantiates models in mem开发者_StackOverflow社区ory to hold the included associated models, such that I can enter model1.associated_models and have it not hit the database again.


Have you considered creating model for database view? For example:

  • Create database view, with your complicated SQL query:

    CREATE VIEW production_plan_items AS
        SELECT * FROM [...]
        INNER JOIN [...];
    
  • Create model for this view:

    # app/view_model.rb
    class ViewModel < ActiveRecord::Base
      self.abstract_class = true
    
      def readonly?
        true
      end   
    
      def before_destroy
        raise ActiveRecord::ReadOnlyRecord
      end 
    end
    
    # app/models/logical/production_plan_item.rb
    module Logical
      class ProductionPlanItem < ::ViewModel
      end
    end
    
  • Use as always, but remember that these records are READ ONLY!

    Logical::ProductionPlanItem.where( ... )
    

If performance still be an issue in the future, you can quite easily convert DB views to materialized views using triggers and stored procedures. This will give your application enormous speed boost, and you don't have to change even one line of Rails code.

Enterprise Rails is highly recommended reading: http://www.amazon.com/Enterprise-Rails-Dan-Chak/dp/0596515200/ref=sr_1_1?ie=UTF8&qid=1293140116&sr=8-1

0

精彩评论

暂无评论...
验证码 换一张
取 消

关注公众号