DataMapper identity map test

gistfile1.rb

require 'rubygems'
require 'dm-core'
require 'dm-migrations'
DataMapper::Logger.new($stdout, :debug)
DataMapper.setup(:default, 'postgres://localhost/test') # createdb test

class Container
  include DataMapper::Resource

  property :id, Serial

  has n, :slots
end

class Slot
  include DataMapper::Resource

  property :id, Serial

  belongs_to :container
  belongs_to :content
end

class Content
  include DataMapper::Resource

  property :id, Serial
  property :data, String

  has n, :slot
end

DataMapper.finalize

DataMapper.auto_migrate!

3.times {|x| Content.create(:data => "hello#{x}") }
2.times do
  Container.create.tap do |container|
    container.slots.create(:content => contents.sample)
    container.slots.create(:content => contents.sample)
  end
end

puts "\n\n\n\n"

DataMapper.repository {
  Content.all.to_a
  Container.all.map(&:slots).flatten.map(&:content)
}

# Output is:
# ~ (0.000679) SELECT "id", "data" FROM "contents" ORDER BY "id"
# ~ (0.000392) SELECT "id" FROM "containers" ORDER BY "id"
# ~ (0.000670) SELECT "id", "container_id", "content_id" FROM "slots" WHERE "container_id" IN (1, 2) ORDER BY "id"
# ~ (0.000430) SELECT "id", "data" FROM "contents" WHERE "id" = 2 ORDER BY "id" LIMIT 1
# ~ (0.001075) SELECT "id", "data" FROM "contents" WHERE "id" = 3 ORDER BY "id" LIMIT 1
# ~ (0.000432) SELECT "id", "data" FROM "contents" WHERE "id" = 1 ORDER BY "id" LIMIT 1
# ~ (0.002290) SELECT "id", "data" FROM "contents" WHERE "id" = 2 ORDER BY "id" LIMIT 1
 
# Expected:
# ~ (0.000679) SELECT "id", "data" FROM "contents" ORDER BY "id"
# ~ (0.000392) SELECT "id" FROM "containers" ORDER BY "id"
# ~ (0.000670) SELECT "id", "container_id", "content_id" FROM "slots" WHERE "container_id" IN (1, 2) ORDER BY "id"
# (Contents should be in the identity map, and not be reloaded)