module ActiveRecord::Calculations

def build_count_subquery(relation, column_name, distinct)
  if column_name == :all
    column_alias = Arel.star
    relation.select_values = [ Arel.sql(FinderMethods::ONE_AS_ONE) ] unless distinct
  else
    column_alias = Arel.sql("count_column")
    relation.select_values = [ aggregate_column(column_name).as(column_alias) ]
  end
  subquery_alias = Arel.sql("subquery_for_count")
  select_value = operation_over_aggregate_column(column_alias, "count", false)
  relation.build_subquery(subquery_alias, select_value)
end