class ReeDao::ExtractChanges

def call(table_name, primary_key, hash)
  cached = __ree_dao_cache.get(table_name, primary_key)
  return hash unless cached
  changes = {}
  hash.each do |column, value|
    previous_column_value = cached[column]
    if cached.has_key?(column) && previous_column_value != value
      changes[column] = value
    end
  end
  changes
end