class ArJdbc::MySQL::ExplainSupport::ExplainPrettyPrinter
@private
Public Instance Methods
pp(result, elapsed)
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Pretty prints the result of a EXPLAIN in a way that resembles the output of the MySQL shell:
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| id | select_type | table | type | possible_keys | key | key_len | ref |
rows | Extra |
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| 1 | SIMPLE | users | const | PRIMARY | PRIMARY | 4 | const | 1 | | | 1 |
SIMPLE | posts | ALL | NULL | NULL | NULL | NULL | 1 | Using where |
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2 rows in set (0.00 sec)
This is an exercise in Ruby hyperrealism :).
# File lib/arjdbc/mysql/explain_support.rb, line 30 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(sep = "\n") << sep end
Private Instance Methods
build_cells(items, widths)
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# File lib/arjdbc/mysql/explain_support.rb, line 65 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
build_separator(widths)
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# File lib/arjdbc/mysql/explain_support.rb, line 61 def build_separator(widths) padding = 1; "+#{widths.map { |w| '-' * (w + (padding * 2 )) }.join('+')}+" end
compute_column_widths(result)
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# File lib/arjdbc/mysql/explain_support.rb, line 52 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