diff options
Diffstat (limited to 'activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb')
-rw-r--r-- | activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb b/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb new file mode 100644 index 0000000000..1820853196 --- /dev/null +++ b/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb @@ -0,0 +1,70 @@ +module ActiveRecord + module ConnectionAdapters + module MySQL + class ExplainPrettyPrinter # :nodoc: + # Pretty prints the result of an EXPLAIN in a way that resembles the output of the + # 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 :). + 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 + + private + + 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 + + def build_separator(widths) + padding = 1 + '+' + widths.map {|w| '-' * (w + (padding*2))}.join('+') + '+' + end + + 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.send(justifier, widths[i]) + end + '| ' + cells.join(' | ') + ' |' + end + + def build_footer(nrows, elapsed) + rows_label = nrows == 1 ? 'row' : 'rows' + "#{nrows} #{rows_label} in set (%.2f sec)" % elapsed + end + end + end + end +end |