RG [re-gist?] of dkubb's hotness

#!/usr/bin/env ruby -Ku
 
# encoding: utf-8
 
require 'rubygems'
require 'dm-core'
require 'pp'
 
module DataMapper
  class Collection
    def union(other)
      assert_no_loaded_entries(:union)
      new_collection(query.union(other.query))
    end
 
    alias | union
    alias + union
 
    def intersection(other)
      assert_no_loaded_entries(:intersection)
      new_collection(query.intersection(other.query))
    end
 
    alias & intersection
 
    def difference(other)
      assert_no_loaded_entries(:difference)
      new_collection(query.difference(other.query))
    end
 
    alias - difference
 
    private
 
    def assert_no_loaded_entries(method)
      unless loaded_entries.empty?
        raise ArgumentError, "#{self.class}##{method} cannot be called on a loaded collection"
      end
    end
  end
 
  class Query
    attr_accessor :conditions
 
    def union(other)
      assert_same_options(other)
      query = dup
      query.conditions = query.conditions.union(other.conditions)
      query
    end
 
    alias | union
    alias + union
 
    def intersection(other)
      assert_same_options(other)
      query = dup
      query.conditions = query.conditions.intersection(other.conditions)
      query
    end
 
    alias & intersection
 
    def difference(other)
      assert_same_options(other)
      query = dup
      query.conditions = query.conditions.difference(other.conditions)
      query
    end
 
    alias - difference
 
    private
 
    def assert_same_options(other)
      # TODO: assert all the ivars, aside from @conditions, are identical
    end
 
    module Conditions
      class AbstractOperation
 
        def union(other)
          Operation.new(:or, dup, other.dup)
        end
 
        alias | union
        alias + union
 
        def intersection(other)
          Operation.new(:and, dup, other.dup)
        end
 
        alias & intersection
 
        def difference(other)
          Operation.new(:and, dup, Operation.new(:not, other.dup))
        end
 
        alias - difference
      end
    end
  end
end
 
DataMapper::Logger.new($stdout, :debug)
DataMapper.setup(:default, 'sqlite3:memory:')
 
class Customer
  include DataMapper::Resource
 
  property :id,   Serial
  property :name, String
  property :age,  Integer
 
  has n, :orders
end
 
class Order
  include DataMapper::Resource
 
  property :id,             Serial
  property :reference_code, String
 
  belongs_to :customer
end
 
DataMapper.auto_migrate!
 
customer1 = Customer.create(:name => 'Dan Kubb',  :age => 34)
customer2 = Customer.create(:name => 'Alex Kubb', :age => 2)
 
customer1.orders.create(:reference_code => 'TEST123')
customer2.orders.create(:reference_code => 'TEST321')
 
puts '-' * 80, 'Union:'
pp Customer.all(:name => 'Dan Kubb') | Customer.all(:name => 'Alex Kubb')
pp Customer.all(:name => 'Dan Kubb') + Customer.all(:name => 'Alex Kubb')
 
puts '-' * 80, 'Intersection:'
pp Customer.all(:name => 'Dan Kubb') & Customer.all(:name => 'Alex Kubb')
 
puts '-' * 80, 'Difference:'
pp Customer.all(:name => 'Dan Kubb') - Customer.all(:name => 'Alex Kubb')
 
__END__
 
 ~ (0.000258) SELECT sqlite_version(*)
 ~ (0.002850) DROP TABLE IF EXISTS "customers"
 ~ (0.001784) DROP TABLE IF EXISTS "orders"
 ~ (0.000038) PRAGMA table_info("customers")
 ~ (0.001835) CREATE TABLE "customers" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "name" VARCHAR(50), "age" INTEGER)
 ~ (0.000021) PRAGMA table_info("orders")
 ~ (0.002111) CREATE TABLE "orders" ("id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, "reference_code" VARCHAR(50), "customer_id" INTEGER NOT NULL)
 ~ (0.002192) CREATE INDEX "index_orders_customer" ON "orders" ("customer_id")
 ~ (0.001891) INSERT INTO "customers" ("name", "age") VALUES ('Dan Kubb', 34)
 ~ (0.004047) INSERT INTO "customers" ("name", "age") VALUES ('Alex Kubb', 2)
 ~ (0.003897) INSERT INTO "orders" ("reference_code", "customer_id") VALUES ('TEST123', 1)
 ~ (0.002357) INSERT INTO "orders" ("reference_code", "customer_id") VALUES ('TEST321', 2)
--------------------------------------------------------------------------------
Union:
 ~ (0.000104) SELECT "id", "name", "age" FROM "customers" WHERE ("name" = 'Dan Kubb' OR "name" = 'Alex Kubb') ORDER BY "id"
[#<Customer @id=1 @name="Dan Kubb" @age=34>, #<Customer @id=2 @name="Alex Kubb" @age=2>]
 ~ (0.000096) SELECT "id", "name", "age" FROM "customers" WHERE ("name" = 'Dan Kubb' OR "name" = 'Alex Kubb') ORDER BY "id"
[#<Customer @id=1 @name="Dan Kubb" @age=34>, #<Customer @id=2 @name="Alex Kubb" @age=2>]
--------------------------------------------------------------------------------
Intersection:
 ~ (0.000051) SELECT "id", "name", "age" FROM "customers" WHERE ("name" = 'Dan Kubb' AND "name" = 'Alex Kubb') ORDER BY "id"
[]
--------------------------------------------------------------------------------
Difference:
 ~ (0.000153) SELECT "id", "name", "age" FROM "customers" WHERE ("name" = 'Dan Kubb' AND "name" <> 'Alex Kubb') ORDER BY "id"
[#<Customer @id=1 @name="Dan Kubb" @age=34>]