gistfile1.builder

require 'rubygems'
require 'dm-core'
require 'dm-migrations'
require 'dm-types'

class Simulation
  include DataMapper::Resource

  property :id, UUID, :key => true, :index => true, :default => lambda { UUIDTools::UUID.random_create }

  has n, :outages
end

class Outage
  include DataMapper::Resource

  property :id, Serial

  belongs_to :simulation
end

DataMapper::Logger.new($stdout, :debug)
DataMapper.setup(:default, 'postgres:///test')

DataMapper.auto_migrate!

sim = Simulation.create
sim.outages.create
sim.outages.create
sim.outages.create
sim.outages.create
sim.outages.create
sim.outages.create

puts sim.outages.count

simulation = Simulation.get(sim.id)
puts simulation.outages.count

gistfile2.txt

scrapcoder@scraptop:~$ ruby test.rb 
 ~ (0.000222) SET backslash_quote = off
 ~ (0.000097) SET standard_conforming_strings = on
 ~ (0.000084) SET client_min_messages = warning
 ~ (0.000522) SELECT version()
 ~ (0.000090) SET client_min_messages = warning
 ~ (0.003987) DROP TABLE IF EXISTS "simulations"
 ~ (0.000127) RESET client_min_messages
 ~ (0.000142) SET client_min_messages = warning
 ~ (0.000293) SELECT current_schema()
 ~ (0.004665) SELECT COUNT(*) FROM "information_schema"."tables" WHERE "table_type" = 'BASE TABLE' AND "table_schema" = 'public' AND "table_name" = 'simulations'
 ~ (0.005225) CREATE TABLE "simulations" ("id" VARCHAR(36) NOT NULL, PRIMARY KEY("id"))
 ~ (0.001874) CREATE INDEX "index_simulations_id" ON "simulations" ("id")
 ~ (0.000176) RESET client_min_messages
 ~ (0.000091) SET client_min_messages = warning
 ~ (0.003477) DROP TABLE IF EXISTS "outages"
 ~ (0.000120) RESET client_min_messages
 ~ (0.000143) SET client_min_messages = warning
 ~ (0.001163) SELECT COUNT(*) FROM "information_schema"."tables" WHERE "table_type" = 'BASE TABLE' AND "table_schema" = 'public' AND "table_name" = 'outages'
 ~ (0.005118) CREATE TABLE "outages" ("id" SERIAL NOT NULL, "simulation_id" VARCHAR(36) NOT NULL, PRIMARY KEY("id"))
 ~ (0.001907) CREATE INDEX "index_outages_simulation" ON "outages" ("simulation_id")
 ~ (0.000178) RESET client_min_messages
 ~ (0.001008) INSERT INTO "simulations" ("id") VALUES ('b1051a24-f06c-46ec-9fa6-7791a5113000')
 ~ (0.001214) INSERT INTO "outages" ("simulation_id") VALUES ('b1051a24-f06c-46ec-9fa6-7791a5113000') RETURNING "id"
 ~ (0.000731) INSERT INTO "outages" ("simulation_id") VALUES ('b1051a24-f06c-46ec-9fa6-7791a5113000') RETURNING "id"
 ~ (0.000531) INSERT INTO "outages" ("simulation_id") VALUES ('b1051a24-f06c-46ec-9fa6-7791a5113000') RETURNING "id"
 ~ (0.000485) INSERT INTO "outages" ("simulation_id") VALUES ('b1051a24-f06c-46ec-9fa6-7791a5113000') RETURNING "id"
 ~ (0.000501) INSERT INTO "outages" ("simulation_id") VALUES ('b1051a24-f06c-46ec-9fa6-7791a5113000') RETURNING "id"
 ~ (0.000501) INSERT INTO "outages" ("simulation_id") VALUES ('b1051a24-f06c-46ec-9fa6-7791a5113000') RETURNING "id"
6
 ~ (0.000769) SELECT "id" FROM "simulations" WHERE "id" = 'b1051a24-f06c-46ec-9fa6-7791a5113000' ORDER BY "id" LIMIT 1
0