Use class objects rather than strings for the dispatch cache

The only reason we're using strings is to pre-populate the cache, but
`Class#name` returns a new string instance on every call. This is a
pretty major source of memory usage. We don't technically need to
pre-populate the cache, and not doing so allows us to go back to using
cache objects

2 files changed, 10 insertions, 18 deletions

diff --git a/lib/arel/visitors/reduce.rb b/lib/arel/visitors/reduce.rb
index 1d74934fe5..9670cad27c 100644
--- a/lib/arel/visitors/reduce.rb
+++ b/lib/arel/visitors/reduce.rb
@@ -10,14 +10,14 @@ module Arel
       private
 
       def visit object, collector
-        send dispatch[object.class.name], object, collector
+        send dispatch[object.class], object, collector
       rescue NoMethodError => e
-        raise e if respond_to?(dispatch[object.class.name], true)
+        raise e if respond_to?(dispatch[object.class], true)
         superklass = object.class.ancestors.find { |klass|
-          respond_to?(dispatch[klass.name], true)
+          respond_to?(dispatch[klass], true)
         }
         raise(TypeError, "Cannot visit #{object.class}") unless superklass
-        dispatch[object.class.name] = dispatch[superklass.name]
+        dispatch[object.class] = dispatch[superklass]
         retry
       end
     end
diff --git a/lib/arel/visitors/visitor.rb b/lib/arel/visitors/visitor.rb
index 2152da9f05..bfe7342f04 100644
--- a/lib/arel/visitors/visitor.rb
+++ b/lib/arel/visitors/visitor.rb
@@ -12,17 +12,9 @@ module Arel
       private
 
       def self.dispatch_cache
-        dispatch = Hash.new do |hash, class_name|
-          hash[class_name] = "visit_#{(class_name || '').gsub('::', '_')}"
+        Hash.new do |hash, klass|
+          hash[klass] = "visit_#{(klass.name || '').gsub('::', '_')}"
         end
-
-        # pre-populate cache. FIXME: this should be passed in to each
-        # instance, but we can do that later.
-        self.class.private_instance_methods.sort.each do |name|
-          next unless name =~ /^visit_(.*)$/
-          dispatch[$1.gsub('_', '::')] = name
-        end
-        dispatch
       end
 
       def get_dispatch_cache
@@ -34,14 +26,14 @@ module Arel
       end
 
       def visit object
-        send dispatch[object.class.name], object
+        send dispatch[object.class], object
       rescue NoMethodError => e
-        raise e if respond_to?(dispatch[object.class.name], true)
+        raise e if respond_to?(dispatch[object.class], true)
         superklass = object.class.ancestors.find { |klass|
-          respond_to?(dispatch[klass.name], true)
+          respond_to?(dispatch[klass], true)
         }
         raise(TypeError, "Cannot visit #{object.class}") unless superklass
-        dispatch[object.class.name] = dispatch[superklass.name]
+        dispatch[object.class] = dispatch[superklass]
         retry
       end
     end