Datamapper DataMapper

Simple model:

class Component
  include DataMapper::Resource
  has n, :alias
end

Sample Merb interpreter + SQL output:

>> cs = Component.all; nil
=> nil
>> cs.length
=> 11
>> cs.each { |c| puts c.id; x = c.aliases.to_a }; nil
 ~ SELECT "id", "created_at", "updated_at", "title" FROM "components" ORDER BY "id"
1
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4, 10, 1, 7, 6, 3, 9, 2, 8, 5, 11)) ORDER BY "id"
2
3
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4, 10, 1, 7, 6, 3, 9, 2, 8, 5, 11)) ORDER BY "id"
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (3)) ORDER BY "id"
4
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4, 10, 1, 7, 6, 3, 9, 2, 8, 5, 11)) ORDER BY "id"
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4)) ORDER BY "id"
5
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4, 10, 1, 7, 6, 3, 9, 2, 8, 5, 11)) ORDER BY "id"
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (5)) ORDER BY "id"
6
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4, 10, 1, 7, 6, 3, 9, 2, 8, 5, 11)) ORDER BY "id"
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (6)) ORDER BY "id"
7
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4, 10, 1, 7, 6, 3, 9, 2, 8, 5, 11)) ORDER BY "id"
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (7)) ORDER BY "id"
8
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4, 10, 1, 7, 6, 3, 9, 2, 8, 5, 11)) ORDER BY "id"
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (8)) ORDER BY "id"
9
10
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4, 10, 1, 7, 6, 3, 9, 2, 8, 5, 11)) ORDER BY "id"
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (10)) ORDER BY "id"
11
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (4, 10, 1, 7, 6, 3, 9, 2, 8, 5, 11)) ORDER BY "id"
 ~ SELECT "id", "created_at", "updated_at", "title", "component_id", "producer_id" FROM "component_aliases" WHERE ("component_id" IN (11)) ORDER BY "id"
=> nil

Wow! Why isn't the identity map or the eager association loading catching this? And why two queries for each access, one of which is covered by the previous one?