Rails - May 2007 - Problem loading associated instances after deserialization

Hi,

I''m not sure if this is an active record bug, but the problem is as
follows:
I''m trying to create a cache of results for an expensive computation.
I''m storing
results to database.

Results contain child objects through has_many association. Storing
data to cache seems to work fine, as well as reading data SEEMS to work
if I use object.inspect method, but when I try to read child objects
of any item found in the cache it doesn''t work (it always returns an
empty array).

A contrived example of what happens:

class MyMeasurementCache

  # each item contains multiple measurements
  # each measurement has_many results
  serialize :items_measurements

  def MyMeasurementCache.run_measurements(items)
    ...
    cache = find_existing_or_create_new(compute_digest(items))
    if cache.hit?
      items.zip(cache.items_measurements).each do |item, measurements|
        item.measurements = measurements
        # now if I inspect item.measurements, I see results in inspect:
        # item.measurements.inspect
        # <MeasurementTypeFoo:0x14c034d8
@attributes={"item_id"=>nil,
        # @results=[#<Result:0x14c03744 @attributes={...}...]
        # however, the following always returns an empty array:
        item.measurements.each do |meas|
           meas.results # always empty
        end
      end
    else
      # not found from cache, store measurements
      cache.items_measurements = items.map { |i| measure_item(i) }
      ...
    end
  end
end

-- 
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