Extension to Ruport's Data::Table to do in-memory joins

data_table.rb

class Ruport::Data::Table

  def left_outer_join(right_table, field)
    left_table = self
    result = left_table.sub_table { |row| false }
    
    new_col_names = right_table.column_names.reject { |i| i == field.to_s }
    result.add_columns new_col_names

    right_table_by_field = {}
    right_table.each { |right_row|
      right_table_by_field[right_row.send(field)] = []  if right_table_by_field[right_row.send(field)].nil?
      right_table_by_field[right_row.send(field)] << right_row
    }

    left_table.each { |left_row|      
      if right_row_matches = right_table_by_field[left_row.send(field)]
        right_row_matches.each { |right_matching_row|
          result << left_row.data.merge(right_matching_row)
        }
      else
        result << left_row.data
      end
    }
    
    result
  end

  def left_outer_join!(right_table, field)
    result = self.left_outer_join(right_table, field)
    @column_names = result.column_names
    @data = result.data
    self
  end

end