Blueprint_component.rb

class BlueprintComponent < ActiveRecord::Base
	self.table_name = "industryActivityMaterials"
	self.primary_key = "typeID"
	
	belongs_to :blueprint, :foreign_key => 'typeID'
	belongs_to :item, :class_name => 'Item', :foreign_key => 'materialTypeID'
end

Output

2.2.1 :042 > BlueprintComponent.limit(25).includes(:item).each do |a| a.item end
  BlueprintComponent Load (0.4ms)  SELECT  `industryActivityMaterials`.* FROM `industryActivityMaterials` LIMIT 25
  Item Load (0.4ms)  SELECT `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` IN (38, 34, 20411, 20418)
  Item Load (0.5ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 35 LIMIT 1
  Item Load (0.3ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 36 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 37 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 38 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 39 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 25887 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 34 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 35 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 36 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 37 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 38 LIMIT 1
  Item Load (0.3ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 39 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 25887 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 34 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 35 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 36 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 37 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 38 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 39 LIMIT 1
  Item Load (0.2ms)  SELECT  `invTypes`.* FROM `invTypes` WHERE `invTypes`.`typeID` = 40 LIMIT 1