Oga will soon have a new XPath compiler that will compile XPath to Ruby source code. This is a quick experiment to see if this would bring any performance increases and if so, how much.

output.txt

Calculating -------------------------------------
           evaluator     1.097k i/100ms
           generated     8.711k i/100ms
-------------------------------------------------
           evaluator     10.641k (±13.5%) i/s -     52.656k
           generated     99.626k (± 1.1%) i/s -    505.238k

Comparison:
           generated:    99626.2 i/s
           evaluator:    10641.4 i/s - 9.36x slower

test.rb

$:.unshift(File.expand_path('../lib', __FILE__))

require 'oga'
require 'benchmark/ips'

document = Oga.parse_xml <<-EOF
<people>
  <person>
    <name>Alice</name>
    <age>26</age>
  </person>

  <person>
    <name>Bob</name>
    <age>27</age>
  </person>

  <person>
    <name>Eve</name>
    <age>25</age>
  </person>
</people>
EOF

expression = 'people/person[name = "Alice"]'

# This would basically be the code Oga's new XPath compiler would generate for
# the above expression. Since there's no compiler just yet this is written by
# hand instead.
generated = proc do |root|
  matched = Oga::XML::NodeSet.new

  root.children.each do |n1|
    if n1.is_a?(Oga::XML::Element) and n1.name == 'people'
      n1.children.each do |n2|
        if n2.is_a?(Oga::XML::Element) and n2.name == 'person'
          n2.children.each do |n3|
            if n3.is_a?(Oga::XML::Element) and n3.name == 'name'
              if n3.text == 'Alice'
                matched << n2
              end
            end
          end
        end
      end
    end
  end

  matched
end

Benchmark.ips do |bench|
  bench.report 'evaluator' do
    Oga::XPath::Evaluator.new(document).evaluate(expression)
  end

  bench.report 'generated' do
    generated.call(document)
  end

  bench.compare!
end