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# frozen_string_literal: true
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
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