module DBBinarySearch

# File lib/db_binary_search.rb, line 8
def self.binary_search(column, value, lower_id=nil, upper_id=nil)
  lower_id = self.first.id unless lower_id
  upper_id = self.last.id unless upper_id

  if lower_id >= upper_id
    return upper_id
  else
    mid_id = lower_id + ((upper_id - lower_id) / 2.0).floor
    row = where(["`#{primary_key}` >= ?", mid_id]).limit(1).first

    return upper_id unless row

    column_value = row.send(column)

    if column_value > value
      return binary_search(column, value, lower_id, mid_id)
    elsif column_value < value
      return binary_search(column, value, mid_id + 1, upper_id)
    else
      return mid_id
    end
  end
end