Class: ActiveRecord::ConnectionAdapters::MySQL::ExplainPrettyPrinter

Do not use. This class is for internal use only.

Relationships & Source Files
Inherits:	Object
Defined in:	activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb

Instance Method Summary

#pp(result, elapsed)

Pretty prints the result of an EXPLAIN in a way that resembles the output of the ::ActiveRecord::ConnectionAdapters::MySQL shell:
#build_cells(items, widths) private
#build_footer(nrows, elapsed) private
#build_separator(widths) private
#compute_column_widths(result) private

Instance Method Details

#build_cells(items, widths) (private)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb', line 54


def build_cells(items, widths)
  cells = []
  items.each_with_index do |item, i|
    item = "NULL" if item.nil?
    justifier = item.is_a?(Numeric) ? "rjust" : "ljust"
    cells << item.to_s.public_send(justifier, widths[i])
  end
  "| " + cells.join(" | ") + " |"
end

#build_footer(nrows, elapsed) (private)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb', line 64


def build_footer(nrows, elapsed)
  rows_label = nrows == 1 ? "row" : "rows"
  "#{nrows} #{rows_label} in set (%.2f sec)" % elapsed
end

#build_separator(widths) (private)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb', line 49


def build_separator(widths)
  padding = 1
  "+" + widths.map { |w| "-" * (w + (padding * 2)) }.join("+") + "+"
end

#compute_column_widths(result) (private)

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb', line 40


def compute_column_widths(result)
  [].tap do |widths|
    result.columns.each_with_index do |column, i|
      cells_in_column = [column] + result.rows.map { |r| r[i].nil? ? "NULL" : r[i].to_s }
      widths << cells_in_column.map(&:length).max
    end
  end
end

#pp(result, elapsed)

Pretty prints the result of an EXPLAIN in a way that resembles the output of the ::ActiveRecord::ConnectionAdapters::MySQL shell:

{-----------------------------------------------------------------------------+-------------}
| id | select_type | table | type  | possible_keys | key     | key_len | ref   | rows | Extra       |
{-----------------------------------------------------------------------------+-------------}
|  1 | SIMPLE      | users | const | PRIMARY       | PRIMARY | 4       | const |    1 |             |
|  1 | SIMPLE      | posts | ALL   | NULL          | NULL    | NULL    | NULL  |    1 | Using where |
{-----------------------------------------------------------------------------+-------------}
2 rows in set (0.00 sec)

This is an exercise in Ruby hyperrealism :).

[ GitHub ]

# File 'activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb', line 19


def pp(result, elapsed)
  widths    = compute_column_widths(result)
  separator = build_separator(widths)

  pp = []

  pp << separator
  pp << build_cells(result.columns, widths)
  pp << separator

  result.rows.each do |row|
    pp << build_cells(row, widths)
  end

  pp << separator
  pp << build_footer(result.rows.length, elapsed)

  pp.join("\n") + "\n"
end