Optimise named route generation when using positional arguments. Closes #9450 [Koz]

  This change delivers significant performance benefits for the most
  common usage scenarios for modern rails applications by avoiding the
  costly trip through url_for.  Initial benchmarks indicate this is
  between 6 and 20 times as fast.


git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7421 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 99 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller/routing_optimisation.rb b/actionpack/lib/action_controller/routing_optimisation.rb
new file mode 100644
index 0000000000..535f1bed63
--- /dev/null
+++ b/actionpack/lib/action_controller/routing_optimisation.rb
@@ -0,0 +1,99 @@
+module ActionController
+  module Routing
+    # Much of the slow performance from routes comes from the 
+    # complexity of expiry, :requirements matching, defaults providing
+    # and figuring out which url pattern to use.  With named routes 
+    # we can avoid the expense of finding the right route.  So if 
+    # they've provided the right number of arguments, and have no
+    # :requirements, we can just build up a string and return it.
+    # 
+    # To support building optimisations for other common cases, the 
+    # generation code is seperated into several classes 
+    module Optimisation
+      def generate_optimisation_block(route, kind)
+        return "" unless route.optimise?
+        OPTIMISERS.inject("") do |memo, klazz|
+          optimiser = klazz.new(route, kind)
+          memo << "return #{optimiser.generation_code} if #{optimiser.guard_condition}\n"
+        end
+      end
+
+      class Optimiser
+        attr_reader :route, :kind
+        def initialize(route, kind)
+          @route = route
+          @kind  = kind
+        end
+
+        def guard_condition
+          'false'
+        end
+
+        def generation_code
+          'nil'
+        end
+      end
+
+      # Given a route:
+      # map.person '/people/:id'
+      #
+      # If the user calls person_url(@person), we can simply
+      # return a string like "/people/#{@person.to_param}" 
+      # rather than triggering the expensive logic in url_for
+      class PositionalArguments < Optimiser
+        def guard_condition
+          number_of_arguments = route.segment_keys.size
+          # if they're using foo_url(:id=>2) it's one 
+          # argument, but we don't want to generate /foos/id2
+          if number_of_arguments == 1
+            "args.size == 1 && !args.first.is_a?(Hash)"
+          else
+            "args.size == #{number_of_arguments}"
+          end
+        end
+
+        def generation_code
+          elements = []
+          idx = 0
+
+
+          if kind == :url
+            elements << '#{request.protocol}'
+            elements << '#{request.host_with_port}'
+          end
+
+          # The last entry in route.segments appears to
+          # *always* be a 'divider segment' for '/'
+          # but we have assertions to ensure that we don't
+          # include the trailing slashes, so skip them
+          route.segments[0..-2].each do |segment|
+            if segment.is_a?(DynamicSegment)
+              elements << "\#{URI.escape(args[#{idx}].to_param, ActionController::Routing::Segment::UNSAFE_PCHAR)}"
+              idx += 1
+            else
+              elements << segment.to_s
+            end
+          end
+          %("#{elements * ''}")
+        end
+      end
+
+      # This case is mostly the same as the positional arguments case
+      # above, but it supports additional query parameters as the last 
+      # argument
+      class PositionalArgumentsWithAdditionalParams < PositionalArguments
+        def guard_condition
+          "args.size == #{route.segment_keys.size + 1}"
+        end
+
+        # This case uses almost the Use the same code as positional arguments, 
+        # but add an args.last.to_query on the end
+        def generation_code
+          super.insert(-2, '?#{args.last.to_query}')
+        end
+      end
+
+      OPTIMISERS = [PositionalArguments, PositionalArgumentsWithAdditionalParams]
+    end
+  end
+end
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