Merge branch 'autocomplete-performance' into 'master'

Improving autocomplete performance part 2

Related issue: gitlab-org/gitlab-ce#3507

See merge request !2253

lib/banzai/filter/abstract_reference_filter.rb

@@ -47,7 +47,17 @@ module Banzai
         { object_sym => LazyReference.new(object_class, node.attr(data_reference)) }
       end
 
-      delegate :object_class, :object_sym, :references_in, to: :class
+      def object_class
+        self.class.object_class
+      end
+
+      def object_sym
+        self.class.object_sym
+      end
+
+      def references_in(*args, &block)
+        self.class.references_in(*args, &block)
+      end
 
       def find_object(project, id)
         # Implement in child class

lib/banzai/filter/redactor_filter.rb

@@ -10,7 +10,7 @@ module Banzai
     #
     class RedactorFilter < HTML::Pipeline::Filter
       def call
-        doc.css('a.gfm').each do |node|
+        Querying.css(doc, 'a.gfm').each do |node|
           unless user_can_see_reference?(node)
             # The reference should be replaced by the original text,
             # which is not always the same as the rendered text.

lib/banzai/filter/reference_filter.rb

@@ -124,7 +124,7 @@ module Banzai
       def replace_link_nodes_with_text(pattern)
         return doc if project.nil?
 
-        doc.search('a').each do |node|
+        doc.xpath('descendant-or-self::a').each do |node|
           klass = node.attr('class')
           next if klass && klass.include?('gfm')
 
@@ -162,7 +162,7 @@ module Banzai
       def replace_link_nodes_with_href(pattern)
         return doc if project.nil?
 
-        doc.search('a').each do |node|
+        doc.xpath('descendant-or-self::a').each do |node|
           klass = node.attr('class')
           next if klass && klass.include?('gfm')
 

lib/banzai/filter/reference_gatherer_filter.rb

@@ -16,7 +16,7 @@ module Banzai
       end
 
       def call
-        doc.css('a.gfm').each do |node|
+        Querying.css(doc, 'a.gfm').each do |node|
           gather_references(node)
         end
 

lib/banzai/querying.rb

+module Banzai
+  module Querying
+    # Searches a Nokogiri document using a CSS query, optionally optimizing it
+    # whenever possible.
+    #
+    # document - A document/element to search.
+    # query    - The CSS query to use.
+    #
+    # Returns a Nokogiri::XML::NodeSet.
+    def self.css(document, query)
+      # When using "a.foo" Nokogiri compiles this to "//a[...]" but
+      # "descendant::a[...]" is quite a bit faster and achieves the same result.
+      xpath = Nokogiri::CSS.xpath_for(query)[0].gsub(%r{^//}, 'descendant::')
+
+      document.xpath(xpath)
+    end
+  end
+end

spec/lib/banzai/querying_spec.rb

+require 'spec_helper'
+
+describe Banzai::Querying do
+  describe '.css' do
+    it 'optimizes queries for elements with classes' do
+      document = double(:document)
+
+      expect(document).to receive(:xpath).with(/^descendant::a/)
+
+      described_class.css(document, 'a.gfm')
+    end
+  end
+end